Thio pyridine N-oxides and regulation of the natural growth and development of plants therewith

ABSTRACT

2-Thio, 2-sulfinyl and 2-sulfonyl pyridine N-oxides of the formula ##STR1## are useful for regulating the natural growth or development of plants. E.g., the compound wherein n = 1, R 1  = methyl and R 2  = 2,3,4-trimethylphenyl retards cotton and increases root growth of turf.

This is a division of application Ser. No. 677,660, filed Apr. 16, 1976, now U.S. Pat. No. 4,050,921.

This invention relates to a method of regulating the natural growth or development of plants using certain 2-substituted pyridine N-oxides, some of which are believed to be new compounds.

Certain of the compounds employed in the present invention are disclosed as herbicides in commonly assigned copending applications Ser. Nos. 559,188 (now U.S. Pat. No. 4,019,893, issued Apr. 26, 1977) and 559,196 (now U.S. Pat. No. 3,960,542 issued June 1, 1976) of Howard L. Plant and Allyn R. Bell, filed March 17, 1975. Other compounds employed herein are disclosed as herbicides in U.S. Pat. Nos. 3,107,994, Rawling et al., Oct. 22, 1963 and 3,155,671, D'Amico, Nov. 3, 1964, or as pharmaceuticals in U.S. Pat. No. 3,772,307, Kaminsky et al., Nov. 13, 1975. However, the non-herbicidal treatment of plants with the presently employed compounds has not heretofore been disclosed, insofar as the present inventors are aware. Certain compounds, to be pointed out hereinbelow, are new chemicals.

In the light of present and future world food problems the necessity to increase productivity in terms of plant efficiency is of paramount importance. Chemical manipulation of plant metabolism to produce desirable results as needed is an effective answer to the situation.

The present invention surprisingly makes it possible to increase the efficiency of photosynthesis by reducing photorespiration. Improvement in yield of major crops such as soybeans, peanuts, cereal grains and cotton can therefore be achieved by more efficient conversion of CO₂ into organic compounds by these plants. The method of the invention in general involves regulating the natural growth or development of plants, by applying to said plants an effective plant-regulating amount of a 2-thio-, 2-sulfinyl-, or 2-sulfonyl-pyridine N-oxide of the following formula I: ##STR2## wherein:

N IS 0, 1 OR 2;

R₁ is hydrogen, alkyl (C₁ to C₁₅), phenyl or benzyl;

R₂ is hydrogen, alkyl (C₁ to C₁₂), alkenyl (C₁ to C₄), alkoxycarbonyl (C₂ or C₃), alicyclic (C₅ or C₆), phenyl, phenyl substituted with from 1 to 5 substituents which may be the same or different and are selected from the group consisting of lower alkyl (C₁ to C₃), halogen, cyano, nitro, alkoxy (C₁ or C₂), phenoxy, dioxymethylene and 2,2-dichlorocyclopropyl; 1-methyl-2,2-dichlorocyclopropyl, 2,2-dichlorocyclopropyl, polycyclic (naphthyl, anthryl), biphenyl, heterocyclic or benzyl;

R₁ and R₂ may be joined together in the form of a polymethylene chain --(CH₂)_(m) -- where m is 3, 4 or 5 to form a carbocyclic ring;

and when R₁ is hydrogen or methyl R₂ can be the radical ##STR3## where y is 0, 1 or 2 and the X's are the same or different and are selected from lower alkyl (C₁ to C₃), halogen, and 2,2-dichlorocyclopropyl.

Certain highly desirable sulfides having the above structure are believed to be new chemical compounds, namely, those of the following formula II: ##STR4## wherein R₁ is C₃ to C₁₅ alkyl; and

R₂ is 2-naphthyl, phenyl, or phenyl substituted with from 1 to 3 substituents which may be the same or different selected from methyl, chlorine and phenoxy.

The new chemicals of formula II include compounds that are remarkable in certain aspects of their activity.

The compounds employed in this invention, as defined by the above formula, to influence the natural growth or development of plant life have been found to be surprisingly effective plant regulators. It is to be understood that the term "plant regulator" is used herein in its common usage and means a substance which, through physiological action, will accelerate or retard the rate of growth or rate of maturation or otherwise alter the behavior of ornamental or crop plants or the product thereof. Thus, the usage herein conforms to the definitions provided by Congress in Public Law 92-516, the Federal Environmental Pesticide Control Act of 1972, section 2, subsection v, wherein the term "plant regulator" is defined as any substance or mixture of substances intended, through physiological action, for accelerating or retarding the rate of growth or rate of maturation, or for otherwise altering the behavior of plants or the produce thereof, but shall not include substances to the extent that they are intended as plant nutrients, trace elements, nutritional chemicals, plant inoculants, and soil amendments (see also U.S. Pat. No. 3,904,395, Eilrich et al., Sept. 9, 1975).

Thus, in accordance with this invention a method is provided whereby viable plants are treated with a chemical substance which alters their natural growth or development to enhance various agricultural or horticultural features of the plants. As employed herein, the term "natural growth or development" designates the normal life cycle of the plant in accordance with its genetics and its environment, in the absence of artificial, external influences.

The term "active ingredient" will be used hereinafter in this specification to connote one or more of the compounds of the above formula.

It is to be understood that the regulation of natural growth and development does not include killing or herbicidal action. Although phytotoxic or lethal amounts of the active ingredient might be employed to destroy certain plants, it is contemplated here to employ only such amounts of said active ingredient as will serve to regulate the natural growth and development of useful plants without substantial injury. As may be expected, and as long understood by those skilled in the art, such effective plant regulating amounts will vary, not only with the particular active ingredient selected for treatment, but also with the regulatory effect to be achieved, the species of plant being treated and its stage of development, and whether a permanent or transient regulating effect is sought. Other factors which may bear upon the determination of an appropriate plant regulating amount include the plant growth medium, the manner in which the treatment is to be applied, weather conditions such as temperature or rainfall, and the like.

In accordance with the instant invention it has been found that desirable regulation of natural plant growth or development is achieved by application of the active ingredient to plants in various states of development. It will be understood that such expressions as "applying to plants" as used herein include applying to plant parts (e.g., seeds) and extend to indirect application (i.e., applying to soil in which the plant is growing or is to be grown) as well as direct application. Thus, the compounds can advantageously be used as a seed treatment. They can be applied to the soil, and seed or transplants planted in the treated soil, or applied to the plant in the seedling stage, flowering stage or fruiting stage and the like, or can be applied to plants at more than one stage of development. Such application may be made directly to one or more of the plant's parts, such as, stems, leaves, flowers, fruit or the like.

Regulation of the natural growth or development of plants by chemical treatment results from the effect of the chemical substance on the physiological processes of the plant and the effect of such substance may be manifested by the morphology of the plant. As should be readily apparent, said regulation may also result from a combined or sequential effect of the chemical manifesting a response in both physiology and morphology.

In general, regulation of the natural growth or development which leads to a morphological change in the plant is readily noticeable by visual observation. Such changes can be found in the size, shape, color or texture of the treated plant or any of its parts. Similarly, changes in the quantity of plant fruit or flowers can be simply noted.

On the other hand, regulation which leads to changes only in the physiological processes occur within the treated plant and are usually hidden from the eye of an observer. Changes of this type are most often in the production, location, storage or use of naturally occurring chemicals, including hormones, within the plant. Physiological changes in a plant often are recognized when followed by a subsequent change in morphology. Additionally, there are numerous analytical procedures known to those skilled in the art for determining the nature and magnitude of changes in the various physiological processes.

The individual compounds employed in the instant invention serve to regulate the natural growth or development of treated plants in a number of diverse ways and it is to be understood that each compound may not produce identical regulatory effects on each plant species or at every rate of application. As stated above, responses will vary in accordance with the compound, the rate, the plant, etc.

One regulatory response demonstrated by the compounds useful in the practice of this invention can be generally termed retardation of vegetative growth and such a response has a wide variety of beneficial features. In certain plants this retardation of vegetative growth causes a diminution or elimination of apical dominance leading to a shorter main stem and increased lateral branching. This regulation of the natural growth or development of plants produces smaller, bushier plants which often demonstrate increased resistance to climatic extremes, pest infestations and the like. Thus, the method of this invention provides for plants that are in a good state of health and tends to produce more effective plants.

The individual compounds employed in this invention regulate the natural growth or development of treated monocotyledonous and dicotyledonous plants in numerous other and different respects. Included among these other regulatory effects are inducing or preventing axillary bud development. The compounds will also promote the abscission of leaves, flowers and fruits. On cotton such a process has the additional benefit of reducing the potential feeding sites of such important insects as the boll weevil and the pink bollworm by either terminating the growth of the plant or by abscissing young fruiting bodies which are a preferred source of food for insects. Other effects include the alteration of shape of canopy, the delay or acceleration of fruit or pod set, etc. Although regulatory effects such as those described above can be desirable, often it is the ultimate result of these effects upon the economic factor which is of primary significance in crop plants or upon the aesthetic factor in ornamental plants. Thus, it must be recognized that increases in yield of individual plants, increases in the yield per unit of cropping area, improvement in the quality of the plants' product, improvement in the plants' vigor and reductions in the cost of harvesting and/or subsequent processing are all of an individual regulatory effect during the growth or development of a plant. Thus, these compounds promote maturity of some plants. This effect is desirable since earlier harvest can be made. This is especially important for cotton in some areas of the United States and other countries.

The practice of the method of this invention is particularly useful for improving the efficiency of row crops such as soybean (Glycine). The application of the 2-thio-, 2-sulfinyl- or 2-sulfonyl-pyridine N-oxides of the above formula to such growing crop plants reduces the stature of the plants without the expected substantial reduction in seed yield. In this manner the plant's efficiency of production is improved and a means is provided for optimizing the crop by increasing the plant population per unit area and treating said crop with the active ingredient during its growing stage. Such reduction in plant stature also increases accessibility to the field for other treatments, cultivation and harvesting.

The productivity of some plants can be increased by controlling photorespiration. About 5 to 10% of the dry matter of plants comes from the minerals and nitrogen of the soil. The balance or 90 to 95% of the dry weight comes from the conversion of CO₂ from the atmosphere by the photosynthetic process. Some plants are efficient converters of CO₂ to dry matter, but many such as soybeans, cotton and the cereals are inefficient users of CO₂. These plants photorespire or release CO₂ under illumination during the daytime. If this loss of CO₂ during the daytime is eliminated in soybeans, a theoretical yield increase of 50% is predicted. The present invention makes it possible to reduce photorespiration with a corresponding increase in yield.

In selecting the appropriate non-herbicidal rate of application of the active ingredient, it will be recognized that precise dosages will be dependent upon the plant species being treated, the development stage of the plant, the particular chemical employed, the mode of application (whether to seed, soil, or directly to the plant itself) and various other factors known to those skilled in the art. In general, the active ingredients are applied to seed, soil or to plants at rates of from about 0.05 to about 10 or more pounds per acre. Foliar applications of from 0.1 to 5 pounds of the active ingredient per acre are preferred.

Manifestations of regulant activity include dark foliar color resulting in a darker green plant indicating higher chlorophyll activity (improved rate of photosynthesis), altered canopy, leaf inhibition or abscission, promotion or prevention of axillary bud development, increased pod set, increased tillering, height reduction, promotion of root growth, improved photosynthetic activity by reducing photorespiration.

By way of non-limiting example, Table I below sets forth a number of plant regulant 2-thio-, 2-sulfinyl and 2-sulfonyl-pyridine N-oxides of the above formula I useful in the invention. Methods of preparing such compounds have been described in copending applications Ser. Nos. 559,188 and 559,196 mentioned above (the disclosures of which are hereby incorporated herein by reference) and U.S. Pat. Nos. 3,107,994, 3,155,671 and 3,772,307 mentioned above, as well as Katritsky and Lagouski--Chemistry of Heterocyclic N-Oxides, Academic Press (1971) (see also U.S. Pat. Nos. 3,005,852, Freyermuth et al., Oct. 24, 1961, 3,006,962, Schultz et al., Oct. 31, 1961 and 3,006,963, Buc et al., Oct. 31, 1961). The sulfides (i.e., the 2-thiopyridine N-oxides) are commonly prepared from 2-chloropyridine N-oxide with a suitable mercaptan and acid acceptor or conversely the sodium salt of 2-mercaptopyridine N-oxide with a suitable halide. The more biologically active sulfoxides (i.e., the 2-sulfinyl pyridine N-oxides) and sulfones (i.e., the 2-sulfonyl pyridine N-oxides) are prepared in the manner described in the aforementioned applications, Ser. Nos. 559,188 and 559,196. In general, the oxidation of the pyridine N-oxide sulfides to sulfoxides and sulfones is accomplished by employing 30 to 50% hydrogen peroxide in a suitable solvent such as acetic acid or water. The peroxy acids such as peracetic, perbenzoic and metachloroperoxybenzoic work well in solvents varying from chloroform and methylene chloride to glacial acetic acid. When hydrogen peroxide is the oxidant of choice then a metallic acid catalyst such as vanadium, tungsten or molybdenum may be used to advantage but is not essential. Certain sulfides of pyridine can be oxidized directly to the pyridine N-oxide sulfone in a single step. The sulfoxides are not available by this technique. Table I gives the systematic name, melting point (uncorrected, taken on an A. H. Thomas apparatus), empirical formula and analysis for a variety of exemplary 2-thio-, 2-sulfinyl- and 2-sulfonyl pyridine N-oxides useful in the invention; an X mark in the last column of Table I, headed "IR", indicates that the structure was confirmed by infrared spectrographic analysis (using a Perkin Elmer Infracord [trademark]). The numbers assigned to the compounds in Table I are used to identify the compounds in subsequent examples.

                                      TABLE I                                      __________________________________________________________________________                                                   Analysis                                                              Empirical                                                                               Calc/Found                       No.        Name                m.p.  Formula   C   H  N  S   IR                __________________________________________________________________________     1  2-(2,2-dichlorocyclopropylmethylsulfinyl)pyridine                                                          Oil   C.sub.9 H.sub.9 Cl.sub.2 NO.sub.2                                                                      X                    N-oxide                                                                     2  2-(phenylmethylthio)pyridine N-oxide                                                                        164-166°                                                                     C.sub.12 H.sub.11 NOS   X                 3  2-(2,2-dichloro-1-methylcyclopropylmethyl-                                                                 93-95 C.sub.10 H.sub.9 Cl.sub.2 NO.sub.3                                                      40.50                                                                              3.72                                                                              4.73                                                                              10.81                                                                               X                    sulfonyl)pyridine N-oxide                  40.51                                                                              3.87                                                                              4.59                                                                              10.94                                                                               X                 4  2-(phenylmethylsulfonyl)pyridine N-oxide                                                                   126-128                                                                              C.sub.12 H.sub.11 NO.sub.3 S                                                                           X                 5  2-(1-naphthylmethylthiopyridine) N-oxide                                                                   130-133                                                                              C.sub.16 H.sub.13 NOS   X                 6  2-(3,4-dimethylphenylmethylsulfonyl)pyridine                                   N-oxide                     165-167                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            60.63                                                                              5.45                                                                              5.05                                                                              11.54                                                                               X                                                               60.77                                                                              5.73                                                                              5.03                                                                              11.71                  7  2-(4-methylphenylmethylsulfonyl)pyridine N-oxide                                                           149-151                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                                           X                 8  2-(4-chlorophenylmethylsulfonyl)pyridine N-oxide                                                           154-155                                                                              C.sub.12 H.sub.11 ClNO.sub.3                                                                           X                 9  2-(1-naphthylmethylsulfonyl)pyridine N-oxide                                                               183-186                                                                              C.sub.13 H.sub.16 NO.sub.3 S                                                                           X                 10 2-(4-chlorophenylmethylthio)pyridine N-oxide                                                               121-123                                                                              C.sub.12 H.sub.10 ClNOS X                 11 2-(4-methylphenylmethylthio)pyridine N-oxide                                                               121-124                                                                              C.sub.13 H.sub.13 NOS   X                 12 2-(4-chlorophenylmethylsulfinyl)pyridine N-oxide                                                           104-107                                                                              C.sub.12 H.sub.10 ClNO.sub.2                                                                           X                 13 2-(2,5-dimethylphenylmethylthio)pyridine N-oxide                                                           141-143                                                                              C.sub.14 H.sub.15 NOS   X                 14 2-(2,5-dimethylphenylmethylsulfonyl)pyridine N-oxide                                                       156-158                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            60.63                                                                              5.45                                                                              5.05                                                                              11.54                                                                               X                                                               60.66                                                                              5.56                                                                              5.18                                                                              11.81                  15 2-(4-nitrophenylmethylsulfonyl)pyridine N-oxide                                                            215-216                                                                              C.sub.12 H.sub.10 N.sub.2 O.sub.5                                                                      X                 16 2-(cyclohexylmethylsulfonyl)pyridine N-oxide                                                                144-145°                                                                     C.sub.12 H.sub.17 NO.sub.3 S                                                                           X                 17 2-(2,2-dichlorocyclopropylmethylsulfonyl)pyridine                                                          103-105                                                                              C.sub.9 H.sub.9 Cl.sub.2 NO.sub.3                                                                      X                    N-oxide                                                                     18 2-(2-ethylphenylmethylthio)pyridine N-oxide                                                                114-118                                                                              C.sub.14 H.sub.15 NOS   X                 19 2-(ethylsulfinyl)pyridine Neoxide                                                                          94-96 C.sub.7 H.sub.9 NO.sub.                                                                                X S               20 2-(2-benzothiazolylmethylsulfonyl)pyridine N-oxide                                                         175-176                                                                              C.sub.13 H.sub.10 N.sub.2 O.sub.3                                              S.sub.2                 X                 21 2-(2-methylphenylmethylthio)pyridine N-oxide                                                               134-136                                                                              C.sub.13 H.sub.13 NOS   X                 22 2-(2-chlorophenylmethylsulfonyl)pyridine N-oxide                                                           151-152                                                                              C.sub.12 H.sub.10 ClNO.sub.3                                                                           X                 23 2-(2-chlorophenylmethylthio)pyridine N-oxide                                                               111-113                                                                              C.sub.12 H.sub.10 ClNOS X                 24 2-(dodecylsulfonyl)pyridine N-oxide                                                                        49-51 C.sub.17 H.sub.29 NO.sub.3 S                                                                           X                 25 2-(dodecylthio)pyridine N-oxide                                                                            87-89 C.sub.17 H.sub.29 NOS   X                 26 2-(1-phenylethylthio)pyridine N-oxide                                                                      112-114                                                                              C.sub.13 H.sub.13 NOS   X                 27 2-(2-methylphenylmethylsulfonyl)pyridine N-oxide                                                           159-161                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                            59.31                                                                              4.93                                                                              5.32    X                                                               59.30                                                                              5.21                                                                              5.31                      28 2-(x,y-dichlorophenylmethylsulfonyl)pyridine N-oxide                                                       132-137                                                                              C.sub.12 H.sub.9 Cl.sub.2                                                                              X                 29 2-(2,6-dichlorophenylmethylthio)pyridine N-oxide                                                           240-241                                                                              C.sub.12 H.sub.9 Cl.sub.2 NOS                                                                          X                 30 2-(2,4,6-trimethylphenylmethylthio)pyridine N-oxide                                                        137-138                                                                              C.sub.15 H.sub.17 NOS   X                 31 2-(2,4,6-trimethylphenylmethylsulfonyl)pyridine                                                            173-175                                                                              C.sub.15 H.sub.17 NO.sub.3 S                                                            61.90                                                                              5.84                                                                              4.81    X                    N-oxide                                    61.97                                                                              5.06                                                                              4.79                      32 2-(2,6-dichlorophenylmethylsulfonyl)pyridine N-oxide                                                       214-216                                                                              C.sub.12 H.sub.9 Cl.sub.2 NO.sub.3                                                      45.37                                                                              2.83                                                                              4.40    X                                                               45.67                                                                              2.89                                                                              4.55                      33 2-([3-trifluoromethylphenyl]methylsulfonyl)                                                                125-127                                                                              C.sub.13 H.sub.10 F.sub.3 NO.sub.3                                                      49.10                                                                              3.16                                                                              4.41    X                    pyridine N-oxide                           48.86                                                                              2.73                                                                              4.20                      34 2-(2,4-dichlorophenylmethylsulfonyl)pyridine N-oxide                                                       154-156                                                                              C.sub.12 H.sub.9 Cl.sub.2 NO.sub.3                                                                     X                 35 2-(1-phenylethylsulfonyl)pyridine N-oxide                                                                  141-143                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                            59.40                                                                              4.95                                                                              5.32    X                                                               59.03                                                                              4.90                                                                              5.35                      36 2-(2,4-dichlorophenylmethylthio)pyridine N-oxide                                                           173-174                                                                              C.sub.12 H.sub.9 Cl.sub.2 NOS                                                                          X                 37 2-([2-methoxy-5-nitrophenyl]methylsulfonyl)                                                                226-227                                                                              C.sub.13 H.sub.10 N.sub.2 O.sub.6                                                                      X                    pyridine N-oxide                                                            38 2-(3,4-dimethylphenylmethylthio)pyridine N-oxide                                                           193-195                                                                              C.sub.14 H.sub.15 NOS   X                 39 2-(isopropenylsulfonyl)pyridine N-oxide                                                                    Oil   C.sub.9 H.sub.11 NO.sub.3 S                                                                            X                 40 2-(phenylethylthio)pyridine N-oxide                                                                        118-120                                                                              C.sub.13 H.sub.13 NOS   X                 41 2-(phenylethylsulfonyl)pyridine N-oxide                                                                     99-100                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                                           X                 42 2-(2,6-dichlorophenylmethylsulfinyl)pyridine                                                               135-137                                                                              C.sub.12 H.sub.9 Cl.sub.2 NO.sub.2                                                      47.65                                                                              2.98                                                                              4.64                         N-oxide                                    47.25                                                                              2.95                                                                              4.25    X                 43 2-(2-fluorophenylmethylthio)pyridine N-oxide                                                               135-137                                                                              C.sub.12 H.sub.13 FNO3  X                 44 2-[(3,4-dioxymethylene-6-chlorophenyl)methyl-                                                              179-180                                                                              C.sub.13 H.sub.10 ClNO.sub.5                                                            47.60                                                                              3.06                                                                              4.28    X                    sulfonyl]pyridine N-oxide                  46.87                                                                              2.83                                                                              4.23                      45 2-(2-fluorophenylmethylsulfonyl)pyridine N-oxide                                                           151-153                                                                              C.sub.12 H.sub.10 FNO.sub.3 S                                                           54.00                                                                              3.74                                                                              5.24    X                                                               54.03                                                                              3.79                                                                              5.32    X                 46 2-(1-ethylpentylsulfonyl)pyridine N-oxide                                                                  Oil   C.sub.12 H.sub.19 NO.sub.3 S                                                                           X                 47 2-(2-ethylphenylmethylsulfonyl)pyridine N-oxide                                                            --    C.sub.14 H.sub.15 NO.sub.3 S                                                                           X                 48 2-(2-hexylsulfonyl)pyridine N-oxide                                                                        71-73 C.sub.12 H.sub.15 NO.sub.3 S                                                                           X                 49 2-(cyclohexylsulfonyl)pyridine N-oxide                                                                     135-138                                                                              C.sub.11 H.sub.15 NO.sub.3 S                                                                           X                 50 2-(2,5-dimethylphenylmethylsulfinyl)pyridine                                                               142-144                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            64.80                                                                              5.64                                                                              5.26    X                    N-oxide                                    64.43                                                                              5.67                                                                              5.13                      51 2-(2-propylthio)pyridine N-oxide                                                                           77-79 C.sub.8 H.sub.11 NOS    X                 52 2-(2-cyanophenylmethylthio)pyridine N-oxide                                                                154-157                                                                              C.sub.13 H.sub.10 N.sub.2 OS                                                                           X                 53 2-(cycloheptylsulfonyl)pyridine N-oxide                                                                    103-107                                                                              C.sub.12 H.sub.17 NO.sub.3 S                                                            56.50                                                                              6.66                                                                              5.50    X                                                               57.14                                                                              6.80                                                                              5.55                      54 2-(2-cyanophenylmethylsulfonyl)pyridine N-oxide                                                            188-190                                                                              C.sub.13 H.sub.10 FN.sub.2 O.sub.3                                                      56.90                                                                              3.65                                                                              10.21   X                                                               57.14                                                                              3.98                                                                              10.22                     55 2-(2-propylsulfonyl)pyridine N-oxide                                                                       110-114                                                                              C.sub.8 H.sub.11 NO.sub.3 S                                                             47.75                                                                              5.51                                                                              6.96    X                                                               47.86                                                                              5.57                                                                              6.78                      56 2-(cycloheptylthio)pyridine N-oxide                                                                        128-131                                                                              C.sub.12 H.sub.17 NOS   X                 57 2-(2,4-dichlorophenylmethylsulfinyl)pyridine                                                               138-141                                                                              C.sub.12 H.sub.9 CL.sub.2 NO.sub.2                                                                     X                    N-oxide                                                                     58 2-(phenylethylsulfinyl)pyridine N-oxide                                                                    Oil   C.sub.13 H.sub.13 NO.sub.2 S                                                                           X                 59 2-[(3-trifluoromethylphenyl)methylsulfinyl]-                                                               104-108                                                                              C.sub.13 N.sub.10 F.sub.3 NO.sub.2                                                      51.80                                                                              3.34                                                                              4.65    X                    pyridine N-oxide                           52.13                                                                              3.35                                                                              4.75                      60 2-(4-methoxyphenylmethylsulfinyl)pyridine N-oxide                                                          140-148                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                                           X                 61 2-(phenylmethylsulfinyl)pyridine N-oxide                                                                   119-122                                                                              C.sub.12 H.sub.11 NO.sub.2 S                                                                           X                 62 2-(3-methylphenylmethylthio)pyridine N-oxide                                                               107-109                                                                              C.sub.13 H.sub.13 NOS   X                 63 2-(3-methylphenylmethylsulfinyl)pyridine N-oxide                                                           67-71 C.sub.13 H.sub.13 NO.sub.2 S                                                            63.20                                                                              5.26                                                                              5.66    X                                                               63.14                                                                              5.71                                                                              5.73                      64 2-(3-methylphenylmethylsulfonyl)pyridine N-oxide                                                           171-173                                                                              C.sub.13 H.sub.13 NO.sub.3 S                                                                           X                 65 2-(2,4,6-trimethylphenylmethylsulfinyl)pyridine                                                            164-166                                                                              C.sub.15 H.sub.17 NO.sub.2 S                                                            65.50                                                                              6.18                                                                              5.09    X                    N-oxide                                    66.11                                                                              6.49                                                                              5.15                      66 2-(2-chlorophenylmethylsulfinyl)pyridine N-oxide                                                           124-127                                                                              C.sub.12 H.sub.10 ClNO.sub.2                                                            53.65                                                                              3.73                                                                              5.22    X                                                               53.91                                                                              4.11                                                                              5.25                      67 2-(3,4-dimethylphenylmethylsulfinyl)pyridine                                                               123-126                                                                              C.sub.14 H.sub.15 NO.sub.2 S                                                            64.43                                                                              5.75                                                                              5.36    X                    N-oxide                                    64.89                                                                              6.08                                                                              5.40                      68 2-(2-methylphenylmethylsulfinyl)pyridine N-oxide                                                            99-102                                                                              C.sub.13 H.sub.13 NO.sub.2 S                                                            63.14                                                                              5.30                                                                              5.66    X                                                               62.66                                                                              5.31                                                                              5.45                      69 2-(2-cyanophenylmethylsulfinyl)pyridine N-oxide                                                            158-161                                                                              C.sub.13 H.sub.10 N.sub.2 O.sub.2                                                       60.45                                                                              3.90                                                                              10.84   X                                                               60.03                                                                              3.86                                                                              10.57                     70 2-(4-methylphenylmethylsulfinyl)pyridine N-oxide                                                           101-103                                                                              C.sub.13 H.sub.13 NO.sub.2 S                                                            63.14                                                                              5.30                                                                              5.66    X                                                               63.57                                                                              5.43                                                                              5.48                      71 2-(3-fluorophenylmethylsulfonyl)pyridine N-oxide                                                           138-140                                                                              C.sub.12 H.sub.10 FNO.sub.3 S                                                                          X                 72 2-(4-fluorophenylmethylsulfinyl)pyridine N-oxide                                                           100-103                                                                              C.sub.12 H.sub.10 FNO.sub.2 S                                                                          X                 73 2-(4-fluorophenylmethylsulfonyl)pyridine N-oxide                                                           136-138                                                                              C.sub.12 H.sub.10 FNO.sub.3 S                                                                          X                 74 2-(3-fluorophenylmethylsulfinyl)pyridine N-oxide                                                           70-74 C.sub.12 H.sub.10 FNO.sub.2 S                                                                          X                 75 2-(2-fluorophenylmethylsulfinyl)pyridine N-oxide                                                           110-113                                                                              C.sub.12 H.sub.10 FNO.sub.2 S                                                           57.40                                                                              3.98                                                                              5.57    X                                                               57.43                                                                              3.95                                                                              5.68                      76 2-(2-oxo-2-phenylethylsulfinyl)pyridine N-oxide                                                            121-123                                                                              C.sub.13 H.sub.11 NO.sub.3 S                                                                           X                 77 2-(2-oxo-2-phenylethylsulfonyl)pyridine N-oxide                                                            117-120                                                                              C.sub.13 H.sub.11 NO.sub.4 S                                                            56.02                                                                              4.05                                                                              5.01    X                                                               56.39                                                                              4.00                                                                              5.05                      78 2-(1-[4-chlorophenyl]ethylthio)pyridine N-oxide                                                            106-108                                                                              C.sub.13 H.sub.12 ClNOS                                                                 58.57                                                                              4.85                                                                              5.14    X                                                               58.81                                                                              5.40                                                                              5.27                      79 2-[1-(4-chlorophenyl)ethylsulfonyl]pyridine N-oxide                                                        188-191                                                                              C.sub.13 H.sub.12 ClNO.sub.3                                                                           X                 80 2-(1-phenylbutylthio)pyridine N-oxide                                                                      130-132                                                                              C.sub.15 H.sub.17 NOS                                                                   69.48                                                                              6.51                                                                              5.46    X                                                               69.43                                                                              6.61                                                                              5.40                      81 2-(1-[2-methylphenyl]ethylthio)pyridine N-oxide                                                            83-85 C.sub.14 H.sub.15 NOS                                                                   68.54                                                                              6.27                                                                              5.45    X                                                               68.56                                                                              6.16                                                                              5.71                      82 2-(pentachlorophenylmethylthio)pyridine N-oxide                                                            183-185                                                                              C.sub.12 H.sub.2 Cl.sub.5 NOS                                                                          X                 83 2-(2,3,6-trichlorophenylmethylthio)pyridine                                                                232-234                                                                              C.sub.12 H.sub.8 Cl.sub.3 NOS                                                                          X                    N-oxide                                                                     84 2-(4-cyanophenylmethylthio)pyridine N-oxide                                                                159-160                                                                              C.sub.13 H.sub.10 N.sub.2 OS                                                                           X                 85 2-(2-oxo-2[p-2',2'-dichlorocyclopropylphenyl]-                                                             163-165                                                                              C.sub.16 H.sub.13 Cl.sub.2 NO.sub.2                                            S                       X                    ethylthio)pyridine N-oxide                                                  86 2-(2-oxo-2[2,4-dimethylphenyl]ethylthio)pyridine                                                           106-108                                                                              C.sub.15 H.sub.15 NO.sub.2 S                                                                           X                    N-oxide                                                                     87 2-(1-[2-naphthyl]ethylthio)pyridine N-oxide                                                                112-115                                                                              C.sub.17 H.sub.15 NOS                                                                   72.94                                                                              5.35                                                                              4.98    X                                                               72.58                                                                              5.37                                                                              4.98                      88 2-(2-methoxy-5-methylphenylmethylsulfonyl)-                                                                115-118                                                                              C.sub.14 H.sub.15 NO.sub.4 S                                                                           X                    pyridine N-oxide                                                            89 2-(2-bromo-5-methoxyphenylmethylsulfonyl)pyridine                                                          157-158                                                                              C.sub.13 H.sub.12 BrNO.sub.4                                                                           X                    N-oxide                                                                     90 2-(pentachlorophenylmethylsulfonyl)pyridine                                                                235-238                                                                              C.sub.12 H.sub.6 Cl.sub.5 NO.sub.3                                                                     X                    N-oxide                                                                     91 2-(pentachlorophenylmethylsulfinyl)pyridine                                                                213-215                                                                              C.sub.12 H.sub.6 Cl.sub.5 NO.sub.2                                                                     X                    N-oxide                                                                     92 2-(2,3,6-trichlorophenylmethylsulfonyl)pyridine                                                            194-196                                                                              C.sub.12 H.sub.8 Cl.sub.3 NO.sub.3                                                                     X                    N-oxide                                                                     94 2-(2,3,6-trichlorophenylmethylsulfinyl)pyridine                                                            168-170                                                                              C.sub.12 H.sub.8 Cl.sub.3 NO.sub.2                                                      42.82                                                                              2.39                                                                              4.16    X                    N-oxide                                    41.89                                                                              2.32                                                                              4.18                      95 2-(4-cyanophenylmethylsulfonyl)pyridine N-oxide                                                            215-217                                                                              C.sub.13 H.sub.10 N.sub.2 O.sub.3                                                                      X                 96 2-(4-cyanophenylmethylsulfinyl)pyridine N-oxide                                                            155-158                                                                              C.sub.13 H.sub.10 N.sub.2 O.sub.2                                                                      X                 97 2-(2-oxo-2[2,4-dimethylphenyl]ethylsulfonyl)pyridine                                                       149-152                                                                              C.sub.15 H.sub.15 NO.sub.4 S                                                                           X                    N-oxide                                                                     98 2-(2-oxo-2[2,4-dimethylphenyl]ethylsulfinyl)-                                                              145-147                                                                              C.sub.15 H.sub.15 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            99 2-(1-[2,5-dimethylphenyl]ethylthio)pyridine N-oxide                                                        118-120                                                                              C.sub.15 H.sub.17 NOS                                                                   69.03                                                                              6.36                                                                              5.21    X                                                               69.48                                                                              6.61                                                                              5.40                      100                                                                               2-(1-[4-bromophenyl]ethylthio)pyridine N-oxide                                                             113-115                                                                              C.sub.13 H.sub.12 BrNOS                                                                 50.20                                                                              4.16                                                                              4.45    X                                                               50.35                                                                              3.90                                                                              4.52                      101                                                                               2-(2,5-diisopropylphenylmethylsulfonyl)pyridine                                                            120-123                                                                              C.sub.18 H.sub.23 NO.sub.3 S                                                            64.84                                                                              6.95                                                                              4.20    X                    N-oxide                                    64.10                                                                              6.89                                                                              4.31                      102                                                                               2-(2,5-diisopropylphenylmethylsulfinyl)pyridine                                                            83-86 C.sub.18 H.sub.23 NO.sub.2 S                                                                           X                    N-oxide                                                                     103                                                                               2-(2-oxo-2[p-2',2'-dichlorocyclopropylphenyl]-                                                             96-99 C.sub.16 H.sub.13 Cl.sub.2 NO.sub.3                                            S        51.94                                                                              3.45                                                                              3.91    X                    ethylsulfonyl)pyridine N-oxide             51.90                                                                              3.54                                                                              3.78                      104                                                                               2-(1-phenylbutylsulfonyl)pyridine N-oxide                                                                  145-148                                                                              C.sub.15 H.sub.17 NO.sub.3 S                                                            61.83                                                                              5.88                                                                              4.89    X                                                               61.53                                                                              5.85                                                                              4.95                      105                                                                               2-[1-(4-methylphenyl)ethylsulfonyl]pyridine                                                                158-160                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            60.35                                                                              5.45                                                                              5.05    X                    N-oxide                                    61.18                                                                              5.70                                                                              5.22                      106                                                                               2-[1-(4-methylphenyl)ethylsulfinyl]pyridine                                                                121-123                                                                              C.sub.14 H.sub.15 NO.sub.2 S                                                                           X                    N-oxide                                                                     107                                                                               2-[1-(2-thienyl)ethylsulfonyl]pyridine N-oxide                                                             147-149                                                                              C.sub.11 H.sub.11 NO.sub.3 S.sub.2                                                      49.05                                                                              4.12                                                                              5.20    X                                                               48.90                                                                              4.39                                                                              5.21                      108                                                                               2-[1-(4-fluorophenyl)ethylsulfonyl]pyridine                                                                142-144                                                                              C.sub.13 H.sub.12 FNO.sub.3 S                                                           55.50                                                                              4.30                                                                              4.98    X                    N-oxide                                    55.47                                                                              4.61                                                                              5.07                      109                                                                               2-[1-(2,5-dimethylphenyl)ethylsulfonyl]pyridine                                                            160-163                                                                              C.sub.15 H.sub.17 NO.sub.3 S                 N-oxide                                                                     110                                                                               2-(1-phenylpropylthio)pyridine N-oxide                                                                     158-160                                                                              C.sub.14 H.sub.15 NOS                                                                   68.51                                                                              6.07                                                                              5.52    X                                                               68.56                                                                              6.16                                                                              5.71                      111                                                                               2-(1-[3,4-dichlorophenyl]ethylthio)pyridine N-oxide                                                        Oil   C.sub.13 H.sub.11 l.sub.2 NOS                                                           52.11                                                                              3.51                                                                              4.94    X                                                               52.05                                                                              3.67                                                                              4.67                      112                                                                               2-(3,4-dioxymethylenephenylmethylthio)pyridine                                                             146-148                                                                              .sub.13 H.sub.11 NO.sub.3 S                                                                            X                    N-oxide                                                                     114                                                                               2-[1-(2-naphthyl)ethylsulfonyl]pyridine N-oxide                                                            144-146                                                                              C.sub.17 H.sub.15 NO.sub.3 S              115                                                                               2-(1-[2,5-dimethylphenyl]octylthio)pyridine                                                                92-94 C.sub.21 H.sub.29 NOS                                                                   73.42                                                                              7.91                                                                              4.18    X                    N-oxide                                    73.44                                                                              8.51                                                                              4.08                      116                                                                               2-(1-(4-bromophenyl)ethylsulfinyl]pyridine N-oxide                                                         177-180                                                                              C.sub.13 H.sub.12 BrNO.sub.2                                                                           X                 117                                                                               2-[1-(4-bromophenyl)ethylsulfonyl]pyridine N-oxide                                                         193-195                                                                              C.sub.13 H.sub.12 BrNO.sub.3                                                            45.63                                                                              3.45                                                                              4.09    X                                                               45.04                                                                              3.32                                                                              4.15                      118                                                                               2-(1-phenylpropylsulfonyl)pyridine N-oxide                                                                 144-146                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            60.63                                                                              5.45                                                                              5.05    X                                                               60.57                                                                              5.39                                                                              5.11                      119                                                                               2-(2-oxo-2-[2,5-dimethylphenyl]ethylthio)-                                                                 63-66 C.sub.15 H.sub.15 NO.sub.2 S                                                            65.90                                                                              6.01                                                                              4.51    X                    pyridine N-oxide                           65.91                                                                              5.53                                                                              5.13                      120                                                                               2-(2-oxo-2{4-fluorophenyl]ethylsulfinyl)pyridine                                                           150-152                                                                              C.sub.13 H.sub.10 FNO.sub.3 S                                                                          X                    N-oxide                                                                     121                                                                               2-(3,4-dichlorophenylmethylsulfinyl)pyridine                                                               133-135                                                                              C.sub.12 H.sub.9 Cl.sub.2 NO.sub.2                                                      47.70                                                                              3.00                                                                              4.64    X                    N-oxide                                    47.44                                                                              2.92                                                                              4.71                      122                                                                               2-(1-[2,5-dimethylphenyl]dodecylthio)pyridine                                                              90-92 C.sub.25 H.sub.37 NOS                                                                   75.19                                                                              9.45                                                                              3.39    X                    N-oxide                                    75.15                                                                              9.33                                                                              3.51                      123                                                                               2-(3-bromophenylmethylthio)pyridine N-oxide                                                                132-134                                                                              C.sub.12 H.sub.10 BrNOS X                 124                                                                               2-(3-bromophenylmethylsulfonyl)pyridine N-oxide                                                            145-147                                                                              C.sub.12 H.sub.10 BrNO.sub.3                                                                           X                 125                                                                               2-(3-bromophenylmethylsulfinyl)pyridine N-oxide                                                            155   C.sub.12 H.sub.10 BrNO.sub.2                                                                           X                 126                                                                               2-(1-[3,4-dihlorophenyl]ethylsulfonyl)pyridine                                                             129-134                                                                              C.sub.13 H.sub.11 Cl.sub.2 NO.sub.3                                            S                       X                    pyridine N-oxide                                                            128                                                                               2-(2-oxo-2-[2,5-dimethylphenyl]ethylsulfinyl)-                                                             153-155                                                                              C.sub.15 H.sub.15 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            129                                                                               2-(3,4-methylenedioxyphenylmethylsulfinyl)-                                                                171-173                                                                              C.sub.13 H.sub.11 NO.sub.4 S                                                                           X                    pyridine N-oxide                                                            130                                                                               2-(3,4-methylenedioxyphenylmethylsulfonyl)-                                                                163-165                                                                              C.sub.13 H.sub.10 NO.sub.5 S                                                                           X                    pyridine N-oxide                                                            131                                                                               2-(2-oxo-2-[2,5-diisopropylphenyl]ethylsulfinyl)-                                                          116-118                                                                              C.sub.19 H.sub.23 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            132                                                                               2-(2-pyridylsulfonyl)propioni acid ethyl ester                                                             109-110                                                                              C.sub.10 H.sub.13 NO.sub.5 S                                                                           X                 133                                                                               2-(2-oxo-2-phenyl-1-methylethylsulfinyl)pyridine                                                           120-124                                                                              C.sub.14 H.sub.13 NO.sub.3 S                                                                           X                    N-oxide                                                                     134                                                                               2-(2-oxo-2-phenyl-1-methylethylsulfonyl)pyridine                                                           179-182                                                                              C.sub.14 H.sub.13 NO.sub.4 S                                                                           X                    N-oxide                                                                     135                                                                               2-(1-[2,3,6-trimethylphenyl]ethylthio)pyridine                                                             108-110                                                                              C.sub.15 H.sub.17 NOS   X                    N-oxide                                                                     136                                                                               2-(2-nitrophenylmethylthio)pyridine N-oxide                                                                120-123                                                                              C.sub.12 H.sub.10 N.sub.2 O.sub.3                                                                      X                 137                                                                               2-(4-[2,2-dichlorocyclopropyl]phneylmethylthio)-                                                           122-127                                                                              C.sub.15 H.sub.13 Cl.sub.2 NOS                                                                         X                    pyridine N-oxide                                                            138                                                                               2-(2,3,6-trimethylphenylsulfonyl)pyridine                                                                  155   C.sub.15 H.sub.17 NO.sub.3 S                                                                           X                    N-oxide                                                                     139                                                                               2-(1-[2,4,6-trimethylphenyl]ethylsulfonyl)-                                                                172-175                                                                              C.sub.16 H.sub.19 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            140                                                                               2-(2-nitrophenylmethylsulfonyl)pyridine N-oxide                                                            155-158                                                                              C.sub.12 H.sub.11 N.sub.2 O.sub.5                                                                      X                 141                                                                               2-(2-nitrophenylmethylsulfinyl)pyridine N-oxide                                                            165-167                                                                              C.sub.12 H.sub.11 N.sub.2 O.sub.3                                                                      X                 142                                                                               2-(2,3,6-trimethylphenylmethylsulfinyl)pyridine                                                            72-75 C.sub.15 H.sub.18 NO.sub.2 S                                                                           X                    N-oxide                                                                     143                                                                               2-(2-methyl-1-naphthylmethylsulfonyl)pyridine                                                              195-198                                                                              C.sub.17 H.sub.16 NO.sub.3 S                                                                           X                    N-oxide                                                                     144                                                                               2-(2-methyl-1-naphthylmethylsulfinyl)pyridine                                                              122-125                                                                              C.sub.17 H.sub.15 NO.sub.2 S                                                                           X                    N-oxide                                                                     145                                                                               2-(α-[2-methylphenyl]phenylmethylsulfonyl)pyridine                                                   122-125                                                                              C.sub.19 H.sub.17 NO.sub.2 S                                                            67.24                                                                              5.05                                                                              4.13    X                    N-oxide                                    66.52                                                                              5.29                                                                              4.13                      146                                                                               2-(2-iodophenylmethylsulfonyl)pyridine N-oxide                                                             142-146                                                                              C.sub.12 H.sub.11 INO.sub.3 S             147                                                                               2-(2-iodophenylmethylsulfinyl)pyridino-N-oxide                                                             160-163                                                                              C.sub.12 H.sub.11 INO.sub.2 S                                                                          X                 148                                                                               2-(1-[4-nitrophenyl]ethylsulfonyl)pyridine N-oxide                                                         167-171                                                                              C.sub.13 H.sub.12 N.sub.2 O.sub.5                                                                      X                 149                                                                               2-(4-[2,2-dichlorocyclopropyl]phenylmethylsul-                                                             oil   C.sub.15 H.sub.13 Cl.sub.2 NO.sub.3                                            S                       X                    fonyl)pyridine N-oxide                                                      150                                                                               2-(4-[2,2-dichlorocyclopropyl]phenylmethylsul-                                                             oil   C.sub.15 H.sub.13 Cl.sub.2 NO.sub.2                                            S                       X                    finyl)pyridine N-oxide                                                      151                                                                               2-(1-[1-naphthyl]ethylsulfonyl)pyridine N-oxide                                                            wax   C.sub.17 H.sub.15 NO.sub.3 S                                                                           X                 152                                                                               2-[1-(1-naphthyl)ethylsulfinyl]pyridine N-oxide                                                            127-130                                                                              C.sub.17 H.sub.15 NO.sub.2 S                                                                           X                 153                                                                               2-(3,4-dimethoxyphenylmethylthio)pyridine N-oxide                                                          141-143                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                            60.73                                                                              5.49                                                                              5.23    X                                                               60.65                                                                              5.45                                                                              5.05                      154                                                                               2-(3,4-dimethoxyphenylmethylsulfinyl)pyridine                                                              133-135                                                                              C.sub.14 H.sub.15 NO.sub.4 S                                                                           X                    N-oxide                                                                     155                                                                               2-(3,4-dimethoxyphenylmethylsulfonyl)pyridine                                                              159-161                                                                              C.sub.14 H.sub.15 NO.sub.5 S                                                                           X                    N-oxide                                                                     156                                                                               2-(1-[2,5-diethylphenyl]ethylsulfonyl)pyridine                                                             124-127                                                                              C.sub.17 H.sub.21 NO.sub.3 S                                                                           X                    N-oxide                                                                     157                                                                               2-(1-[2,5-diisopropylphenyl]ethylthio)pyridine                                                             124-126                                                                              C.sub.19 H.sub.25 NOS                                                                   72.33                                                                              7.75                                                                              4.54    X                    N-oxide                                    72.35                                                                              7.99                                                                              4.44                      158                                                                               2-(cyclopentylsulfinyl)pyridine N-oxide                                                                    80-82 C.sub.10 H.sub.13 NO.sub.2 S                                                                           X                 159                                                                               2-(cyclopentylsulfonyl)pyridine N-oxide                                                                    107-109                                                                              C.sub.10 H.sub.13 NO.sub.3 S                                                                           X                 160                                                                               2-(2,5-dimethoxyphenylmethylsulfonyl)pyridine                                                              129-132                                                                              C.sub.14 H.sub.15 NO.sub.5 S                                                                           X                    N-oxide                                                                     161                                                                               2-(2,5-dimethoxyphenylmethylsulfinyl)pyridine                                                              136-138                                                                              C.sub.14 H.sub.15 NO.sub.4 S                                                                           X                    N-oxide                                                                     162                                                                               2-(2-ethoxyphenylmethylsulfinyl)pyridine                                                                   135-138                                                                              C.sub.14 H.sub.15 NO.sub.3 S                                                                           X                    N-oxide                                                                     163                                                                               2-(2-ethoxyphenylmethylsulfonyl)pyridine                                                                   145-147                                                                              C.sub.14 H.sub.15 NO.sub.4 S                                                                           X                    N-oxide                                                                     164                                                                               2-(1-[2-chloro-4-methylphenyl]ethylthio)-                                                                  118-120                                                                              C.sub.14 H.sub.14 ClNOS                                                                 60.06                                                                              4.98                                                                              5.21    X                    pyridine N-oxide                           60.04                                                                              5.65                                                                              5.00                      165                                                                               2-(1-[2-chloro-4-methylphenyl]ethylsulfonyl)-                                                              166-168                                                                              C.sub. 14 H.sub.14 ClNO.sub.3                                                           53.89                                                                              4.50                                                                              4.48    X                    pyridine N-oxide                           54.00                                                                              4.53                                                                              4.49                      166                                                                               2-(1-[2-chloro-4-methylphenyl]ethylsulfinyl)-                                                              121-123                                                                              C.sub.14 H.sub.14 CNO.sub.2 S                                                           56.74                                                                              4.77                                                                              4.82    X                    pyridine N-oxide                           56.91                                                                              4.77                                                                              4.74                      167                                                                               2-(1-[2-chloro-5-methylphenyl]ethylthio)-                                                                  112-114                                                                              C.sub.14 H.sub.14 ClNOS                                                                 60.45                                                                              5.13                                                                              5.17    X                    pyridine N-oxide                           60.04                                                                              5.65                                                                              5.00                      168                                                                               2-(1-[2,5-diisopropylphenyl]ethylsulfonyl)-                                                                123-127                                                                              C.sub.19 H.sub.25 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            169                                                                               2-(2,3,5,6-tetrachloro-4-methylphenylmethylthio)-                                                          178-180                                                                              C.sub.13 H.sub.9 Cl.sub.4 NOS                                                                          X                    pyridine N-oxide                                                            170                                                                               2-(2,3,5,6-tetrachloro-4-methylphenylmethyl-                                                               204-205                                                                              C.sub.13 H.sub.9 Cl.sub.4 NO.sub.3                                                                     X                    sulfinyl)pyridine N-oxide                                                   171                                                                               2-(2,3,5,6-tetrachloro-4-methylphenylmethyl-                                                               215-218                                                                              C.sub.13 H.sub.9 Cl.sub.4 NO.sub.3                                                                     X                    sulfonyl)pyridine N-oxide                                                   172                                                                               2-(1-[2,5-dichlorophenyl]ethylthio)pyridine                                                                145-147                                                                              C.sub.13 H.sub.11 Cl.sub.2 NOS                                                          52.11                                                                              3.70                                                                               4.54   X                    N-oxide                                    52.01                                                                              3.69                                                                              4.67                      173                                                                               2-(1-[2-chloro-5-methylphenyl]ethylsulfinyl)-                                                              125-127                                                                              C.sub.14 H.sub.14 ClNO.sub.2                                                            57.65                                                                              4.92                                                                              4.71    X                    pyridine N-oxide                           56.91                                                                              4.77                                                                              4.74                      174                                                                               2-(1-[2-chloro-5-methylphenyl]ethylsulfonyl)-                                                              175-177                                                                              C.sub.14 H.sub.14 ClNO.sub.3                                                            54.00                                                                              4.77                                                                              4.42    X                    pyridine N-oxide                           54.00                                                                              4.53                                                                              4.49                      175                                                                               2-(1-[2,5-dichlorophenyl]ethylsulfinyl)pyridine                                                            127-128                                                                              C.sub.13 H.sub.11 Cl.sub.2 NO.sub.2                                            S        49.36                                                                              3.56                                                                              4.37    X                    N-oxide                                    49.36                                                                              3.51                                                                              4.43                      176                                                                               2-(1-[2,5-dichlorophenyl]ethylsulfonyl)pyridine                                                            158-160                                                                              C.sub.13 H.sub.11 Cl.sub.2 NO.sub.3                                            S        47.00                                                                              3.46                                                                              4.17    X                    N-oxide                                    47.00                                                                              3.32                                                                              4.22                      177                                                                               2(1-[2,4,5-trimethylphenyl]ethylsulfinyl)-                                                                 134-137                                                                              C.sub.16 H.sub.19 NO.sub.2 S                                                                           X                    pyridine N-oxide                                                            179                                                                               2-(1-[2,3,4-trimethylphenyl]ethylsulfinyl)-                                                                164-167                                                                              C.sub.16 H.sub.19 NO.sub.2 S                                                                           X                    pyridine N-oxide                                                            180                                                                               2-(1-[2,3,4-trimethylphenyl]ethylsulfonyl)-                                                                155.158                                                                              C.sub.16 H.sub.19 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            181                                                                               2-(1-[2,3,4,5-tetramethylphenyl]ethylsulfinyl)-                                                            185-190                                                                              C.sub.17 N.sub.21 NO.sub.2 S                                                                           X                    pyridine N-oxide                                                            182                                                                               2-(1-[2,3,4,5-tetramethylphenyl]ethylsulfonyl)-                                                            145-150                                                                              C.sub.17 H.sub.21 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            183                                                                               2-(3,4,5-trimethoxyphenylmethylsulfinyl)-                                                                  144-146                                                                              C.sub.15 H.sub.17 NO.sub.5                                                              55.28                                                                              5.25                                                                              4.26    X                    pyridine N-oxide                           55.73                                                                              5.30                                                                              4.33                      184                                                                               2-(3,4,5-trimethoxyphenylmethylsulfonyl)-                                                                  153-155                                                                              C.sub.15 H.sub.17 NO.sub.6 S                                                            53.09                                                                              4.95                                                                              4.10    X                    pyridine N-oxide                           53.10                                                                              5.05                                                                              4.13                      185                                                                               2-(9-anthranylmethylsulfinyl)pyridine N-oxide                                                              150-153                                                                              C.sub.20 H.sub.15 NO.sub.2 S                                                                           X                 186                                                                               2-(2-thienylmethylthio)pyridine N-oxide                                                                    166-170                                                                              C.sub.10 H.sub.9 NOS.sub.2                                                                             X                 187                                                                               2-(2-thienylmethylsulfinyl)pyridine N-oxide                                                                115-119                                                                              C.sub.10 H.sub.9 NO.sub.2 S.sub.2                                                                      X                 188                                                                               2-(2-thienyolmethylsulfonyl)pyridine N-oxide                                                               90-97 C.sub.10 H.sub.9 NO.sub.3 S.sub.2                                                                      X                 189                                                                               2-(1-phenylethylsulfinyl)pyridine N-oxide                                                                  130-131                                                                              C.sub.13 H.sub.13 NO.sub.2 S                                                                           X                 190                                                                               2-(1-[2,5-dimethylphenyl]ethylsulfinyl)pyridine                                                            126-127                                                                              C.sub.15 H.sub.17 NO.sub.2 S                                                                           X                    N-oxide                                                                     191                                                                               2-(1-[4-chlorophenyl 9 ethylsulfinyl)pyridine                                                              130-131                                                                              C.sub.13 H.sub.12 ClNO.sub.2                                                                           X                    N-oxide                                                                     192                                                                               2-(1-[2,4-dichloro-3-methylphenyl]ethylsul-                                                                192-194                                                                              C.sub.14 H.sub.13 Cl.sub.2 NO.sub.3                                            S                       X                    fomyl)pyridine N-oxide                                                      193                                                                               2-(1-[2,4-dichloro-3-methylphenyl]ethylsul-                                                                147-148                                                                              C.sub.15 H.sub.13 Cl.sub.2 NO.sub.                                                                     X                    finyl)pyridine N-oxide                                                      194                                                                               2-(1-phenyl-2-propylthio)pyridine N-oxide                                                                  125-127                                                                              C.sub.14 H.sub.15 NOS   X                 195                                                                               2-(3-methyl-1-[2,5-dimethylphenyl]butyl-                                                                   185-187                                                                              C.sub.18 H.sub.23 NO.sub.3 S                                                                           X                    sulfonyl)pyridine N-oxide                                                   196                                                                               2-(1-phenyl-2-propylsulfonyl)pyridine N-oxide                                                              99-101                                                                               C.sub.14 H.sub.15 NO.sub.3 S                                                                           X                 197                                                                               2-(1-phenyl-2-propylsulfinyl)pyridine N-oxide                                                              Oil   C.sub.14 H.sub.15 NO.sub.2 S                                                                           X                 198                                                                               2-(1-[2,5-dichlorothienyl-3-]ethylthio)pyridine                                                            129-133                                                                              C.sub.11 H.sub.9 Cl.sub.2 NOS.sub.2                                                                    X                    N-oxide                                                                     199                                                                               2-(1-[2,5-dimethylphenyl]-2-phenylethylthio)-                                                              Oil   C.sub.21 H.sub.2 NOS    X                    pyridine N-oxide                                                            200                                                                               2-(4-vinylphenylmethylthio)pyridine N-oxide                                                                103-105                                                                              C.sub.14 H.sub.13 NOS   X                 201                                                                               2-(4-vinylphenylmethylsulfinyl)pyridine N-oxide                                                            Oil   C.sub.14 H.sub.13 NO.sub.2 S                                                                           X                 202                                                                               2-(4-biphenylmethylthio)pyridine N-oxide                                                                   130-132                                                                              C.sub.19 H.sub.17 NOS   X                 203                                                                               2-(1-[4-phenoxyphenyl]ethylthio)pyridine                                                                   Oil   C.sub.19 H.sub.17 NO.sub.2 S                                                                           X                    N-oxide                                                                     204                                                                               2-(1-[4-phenoxyphenyl]ethylsulfonyl)pyridine                                                               Oil   C.sub.19 H.sub.17 NO.sub.4 S                                                                           X                    N-oxide                                                                     205                                                                               2-(-methyl-5-isopropylphenylmethylthio)pyridine                                                            Oil   C.sub.17 H.sub.21 NOS   X                    N-oxide                                                                     206                                                                               2-(2-methyl-5-isopropylphenylmethylsulfonyl)-                                                              Oil   C.sub.17 H.sub.21 NO.sub.3 S                                                                           X                    pyridine N-oxide                                                            207                                                                               2-(1-[5-indanyl]ethylthio)pyridine N-oxide                                                                 Oil   C.sub.16 H.sub.17 NOS   X                 208                                                                               2-(1-[5-indanyl]ethylsulfonyl)pyridine N-oxide                                                             138-140                                                                              C.sub.16 H.sub.17 NO.sub.3 S                                                                           X                 209                                                                               2-(3-methyl-1-[2,5-dimethylphenyl]butylthio)-                                                              Oil   C.sub.18 H.sub.23 NOS   X                    pyridine N-oxide                                                            210                                                                               2-(1-[2,5-dimethylphenyl]butylthio)pyridine                                                                Oil   C.sub.17 H.sub.21 ONS   X                    N-oxide                                                                     212                                                                               2-[1-(p-chlorophenyl)octylthio]pyridine N-oxide                                                            71-73 C.sub.19 H.sub.24 ClNOS X                 213                                                                               2-[1-(p-chlorophenyl)butylthio]pyridine N-oxide                                                            52-54 C.sub.15 H.sub.16 ClNOS X                 214                                                                               2-[1-(p-chlorophenyl)dodecylthio]pyridine N-oxide                                                          69-71 C.sub.23 H.sub.32 ClNOS X                 215                                                                               2-[1-(2-chloro-5-methylphenyl)octylthio)-                                                                  102-104                                                                              C.sub.20 H.sub.26 ClNOS                                                                 66.02                                                                              7.21                                                                              3.85                                                                              8.80 X                    pyridine N-oxide                           66.77                                                                              7.28                                                                              3.75                                                                              8.86                   216                                                                               2-[1-(2-naphthalene)octylthio]pyridine                                                                     75-76 C.sub.23 H.sub.27 NOS                                                                   75.61                                                                              7.45                                                                              3.83                                                                              8.76 X                    N-oxide                                    74.63                                                                              7.35                                                                              3.78                                                                              8.54                   217                                                                               2-[1-(4-phenoxyphenyl)octylthio]pyridine                                                                   91-92 C.sub.25 H.sub.29 NO.sub.2 S                                                            73.71                                                                              7.12                                                                              3.43                                                                              7.86 X                    N-oxide                                    72.77                                                                              7.03                                                                              3.87                                                                              7.68                   218                                                                               2-[1-(3,4,5-trimethylphenyl)octylthio]-                                                                    Oil   C.sub.22 H.sub.31 NOS   X                    pyridine N-oxide                                                            219                                                                               2-[1-(4-chlorophenyl)hexadecylthio]pyridine                                                                65-66 C.sub.27 H.sub.40 ClNOS                                                                 70.20                                                                              8.66                                                                              3.03                                                                              6.93 X                    N-oxide                                    71.29                                                                              9.80                                                                              2.77                                                                              6.09                   220                                                                               2-[1-(2,5-dimethyphenyl)hexadecylthio]-                                                                    81-83 C.sub.29 H.sub.45 NOS                                                                   76.50                                                                              9.96                                                                              3.07                                                                              7.02 X                    pyridine N-oxide                           76.72                                                                              9.83                                                                              3.06                                                                              6.64                   __________________________________________________________________________

The following preparations illustrate methods of making typical compounds of Table I.

Compound 80: 2-(1-Phenylbutylthio)pyridine N-oxide

A mixture of 16.9 gms (0.1 mol) of 1-phenylbutylchloride, 36 gms of a 40% aqueous solution of the sodium salt of 2-mercaptopyridine N-oxide (0.1 mol) and 50 ml of ethanol was warmed and stirred at 50° to 60° C. for 2.5 hours. The cooled reaction mixture was poured into 500 ml of water with agitation. The precipitated product was filtered, washed with water and dried. After recrystallization from ethanol a yield of 10 gms (45% theory) of white crystals was obtained.

Melting point -- 130°-132° C.

Analysis based on C₁₅ H₁₇ NOS: Calc: C 69.48; H 6.61; N 5.40; Found: C 69.48; H 6.51; N 5.46

Compound 139: 2-(1-[2,4,6-Trimethylphenyl]ethylsulfonyl)pyridine N-oxide

To a vigorously stirred mixture of 5.6 gm (0.02 mol) of 2-(1-[2,4,6-trimethylphenyl]ethylthio)pyridine N-oxide in 50 ml of chloroform and 50 ml of phosphate buffer solution (pH 7.5) maintained at 0° to 5° C. is slowly added 8 gm (0.04 mol) metachloroperoxybenzoic acid (85%) (MCPBA) in 100 ml of chloroform. After addition is completed the temperature is allowed to become ambient. Stirring is continued for sixteen hours.

The chloroform layer is separated, washed with sodium bicarbonate solution to remove the benzoic acid and dried over sodium sulfate. Removal of the chloroform yields an oil which crystallizes upon standing. Recrystallization from ethanol yields 3 gms (50% theory) of product.

Melting point 172° - 175° C. IR: SO₂ 1310, 1140; NO 1270, 845 cm⁻¹

Compound 68: 2-(2-Methylphenylmethylsulfinyl)pyridine N-oxide

To a vigorously stirred solution of 6.9 gm (0.03 mol) of 2-(2-methylphenylmethylthio)pyridine N-oxide in 50 ml of chloroform maintained at 0° to 10° C. is slowly added a solution of 6 gm (0.03 mol) MCPBA (85%) in 100 ml of chloroform. When addition is complete the temperature is allowed to rise to ambient. After sixteen hours the reaction solution is washed up in the manner described in Example 139.

The resultant residual oil crystallizes upon standing and after recrystallizing from ethanol, 4.7 gm (58% theory) of product is obtained.

Melting point 99° - 102° C.

Analysis based on C₁₃ H₁₃ NO₂ S-: Calc: C 63.14; H 5.30; N 5.66 Found: C 62.66; H 5.31; N 5.45

Compound 140: 2-(2-Nitrophenylmethylsulfonyl)pyridine N-oxide

The procedure employed is identical to that of Example 139 using 5.2 gm (0.02 mol) 2-(2-nitrophenylmethylthio)pyridine N-oxide in 50 ml chloroform with 5 gms (0.04 mol) MCPBA in 100 ml chloroform.

The crude product which is only sparingly soluble in hot ethanol required 300 ml for recrystallization to yield 5 gms (96% theory) of product.

Melting point 155° - 158° C. IR: SO₂ 1330, 1140; NO 1280, 845 cm⁻¹

Compound 115: 2-(2-[2,5-Dimethylphenyl]octylthio)pyridine N-oxide

A mixture of 24 gm (0.1 mol) of 1-(2,5-dimethylphenyl)n-hexylchloride and 36 gms of a 40% aqueous solution of the sodium salt of 2-mercaptopyridine N-oxide in 50 ml of ethanol is heated with stirring at 60 to 70° for one hour. The ethanol is removed under vacuum and the residual slurry extracted with two 75 ml portions of chloroform. The chloroform solution is dried over sodium sulfate, filtered and evaporated to approximately 30 gms of crude material. Recrystallization from ethyl acetate yields 23 gm (68% theory) of pure product.

Melting point 92° - 94° C. IR: NO 1255, 840; >4CH₂ chain 710 cm⁻¹

Compound 75: 2-(2-Fluorophenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 5.7 gm (0.024 mol) 2-(2-fluorophenylmethylthio)pyridine N-oxide in 50 ml of chloroform with 4.8 gm (0.024 mol) MCPBA in 75 ml chloroform.

The residual crude oil crystallizes upon standing and after recrystallization from ethanol yields 3.8 gm (65% theory) of product.

Melting point 110° - 113° C.

Analysis based on C₁₂ H₁₁ FNO₂ S Calc: C 57.36; H 4.01; N 5.58; Found: C 57.43; H 3.95; N 5.68

Compound 96: 2-(4-Cyanophenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 3.6 gm (0.015 mol) 2-(4-cyanophenylmethylthio)pyridine N-oxide in 50 ml of chloroform with 3 gm (0.015 mol) MCPBA in 50 ml chloroform.

The crude product is recrystallized from ethanol to yield 215 gm (66% theory) of product.

Melting point 155° - 158° C. IR: NO 1240, 840; SO 1045 cm⁻¹

Compound 50: 2-(2,5-Dimethylphenylmethylsulfinyl)pyridine N-oxide.

A vigorously stirred slurry consisting of 30 gm (0.12 mol) 2-(2,5-dimethylphenylthio)pyridine N-oxide in 130 ml of 5% aqeuous acetic acid and 0.03 gm of vanadium pentoxide is brought to 80° C. and 12 gm (0.12 mol) of 30% hydrogen peroxide added slowly. The addition is exothermic necessitating some intermittent cooling to maintain the temperature below 85° C. The addition requires about fifteen minutes during which time the slurry changes to a homogeneous solution. The reaction mixture is cooled down precipitating the solid sulfoxide. Filtration followed by a water wash and drying yielded 30 gm (96% theory) of product.

Melting point 145°-147° C.

Analysis based on C₁₄ H₁₅ NO₂ S: Calc. C 64.34; H 5.75; N 5.36; Found: C 64.43; H 5.67; N 5.13

Compound 62: 2-(3,4-Dimethylphenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 7.4 gm (0.03 mol) 2-(3,4-dimethylphenylmethylthio)pyridine N-oxide in 50 ml of chloroform with 6 gm (0.03 mol) MCPBA (85%) in 100 ml chloroform.

The crude product is recrystallized from ethanol to yield 5.7 gm (75% theory) of product.

Melting point 123°-126° C.

Analysis based on C₁₄ H₁₅ NO₂ S Calc: C 64.34; H 5.75; N 5.36; Found: C 64.89; H 6.08; N 5.50

Compound 128: 2-(2-Oxo-2-[2,5-dimethylphenyl]ethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 8.2 gm (0.03 mol) 2-(2-oxo-2-[2,5-dimethylphenyl]ethylthio)pyridine N-oxide in 50 ml chloroform with 6 gm (0.03 mol) MCPBA (85%) in 100 ml chloroform.

The crude product is recrystallized from ethanol to yield 5.4 gm (64% theory) of product.

Melting point 153°-155° C. (decomp.). IR: C = O 1680, NO 1240, 845, SO 1055, 1075 (doublet) cm⁻¹

Compound 6: 2-(3,4-Dimethylphenylmethylsulfonyl)pyridine N-oxide

Twenty (20) ml (0.2 mol) of 30% hydrogen peroxide is added slowly and with stirring to 11.5 gm (0.05 mol) of 2-(3,4-dimethylphenylmethylthio)pyridine in 50 ml of glacial acetic acid maintained at ambient temperature. After one hour the mixture is gradually heated to 80°-85° C. and maintained for ten hours. Cool and add an equal volume of water. The volume is reduced by one-half by evaporation. When peroxide is detected in the residue with starch iodide paper the dilution and evaporation procedure is repeated, until the peroxide has been removed. Evaporation is then carried to a residual oil which is taken up in 7:3 chloroform:acetone and chromotographed on a silica gel column.

5.5 gms of product is isolated and recrystallized from ethanol (40% theory).

Melting point 165°-167° C.

Analysis based on C₁₄ H₁₅ NO₃ S: Calc: C 60.63; H 5.41; N 5.03; S 11.55; Found: C 60.77; H 5.73; N 4.98; S 11.73

Compound 57: 2-(2,4-Dichlorophenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 5.8 gm (0.02 mol) 2-(2,4-Dichlorophenylmethylthio)pyridine N-oxide in 50 ml of chloroform and 4 gm (0.02 mol) MCPBA in 100 ml of chloroform.

The crude material is recrystallized from ethanol to yield 5.5 gm (90% theory) of pure product. Melting point 138°-141° C. IR Bands NO 1240, 838 CM⁻¹, SO 1050 cm⁻¹.

Compound 138: 2-(2,3,6-Trimethylphenylmethylsulfonyl)pyridine N-oxide

The procedure employed is identical to that of Example 139 using 10.4 gm (0.04 mol) 2-(2,3,6-trimethylphenylmethylthio)pyridine N-oxide in 50 ml of chloroform and 16 gm (0.08 mol) MCPBA in 200 ml of chloroform.

The oily residue from the work-up crystallizes and is recrystallized from ethanol to give 7.9 gm (69% theory) of pure product.

Melting point 153°-155° C.

Analysis based on C₁₅ H₁₇ NO₃ S: Calc: C 61.83; H 5.88; N 4.81; Found: C 61.28; H 5.87; N 4.92

Compound 63: 2-(3-Methylphenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical with that of Example 68 using 4.6 gm (0.02 mol) 2-(3-Methylphenylmethylthio)pyridine N-oxide in 50 ml of chloroform and 4 gm (0.02 mol) MCPBA in 100 ml chloroform.

Crude material is recrystallized from ethylacetate to give 2 gm (45% theory) of pure product.

Melting point 67°-71° C.

Analysis based on C₁₃ H₁₃ NO₂ S: Calc: C 63.20; H 5.26; N 5.66; Found: C 63.14; H 5.71; N 5.73

Compound 60: 2-(4-Methoxyphenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 7 gm (0.028 mol) 2-(4-methoxyphenylmethylthio)pyridine N-oxide in 50 ml of chloroform and 5.6 gm (0.028 mol) MCPBA in 100 ml chloroform.

The crude material is recrystallized from ethanol to give 6 gm (82% theory) of pure product.

Melting point 140°-143° C. IR Bands NO 1250, 835 cm⁻¹, SO 1040

Compound 121: 2-(3,4-Dichlorophenylmethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 8 gm (0.028 mol) B 2-(3,4-dichlorophenylmethylthio)pyridine N-oxide in 50 ml of chloroform and 5.6 gm (0.028 mol) MCPBA in 100 ml chloroform.

The crude material is recrystallized from ethanol to give 5.6 gm (82% theory) of pure product.

Melting point 133°-135° C.

Analysis based on C₁₂ H₉ Cl₂ NO₂ S: Calc: C 47.70; H 3.00; N 6.64; Found: C 47.44; H 2.92; N 4.71

Compound 58: 2-(2-Phenylethylsulfinyl)pyridine N-oxide

The procedure employed is identical to that of Example 68 using 2.8 gm (0.012 mol) 2-(2-phenylethylthio)pyridine N-oxide in 25 ml of chloroform with 2.4 gm (0.012 mol) MCPBA in 50 ml chloroform.

The product is an oil and purity is determined by TLC. Structure is verified by IR.

Significant Bands NO 1250, 845 cm⁻¹, SO 1050 cm⁻¹, 5 ArCH 750, 695 cm⁻¹

Compound 122: 2-(1-[2,5-Dimethylphenyl]dodecylthio)pyridine N-oxide

A mixture of 46.2 gm (0.15 mol) of 1-phenyldodecylchloride, 54 gms of a 40% aqueous solution of the sodium salt of 2-mercaptopyridine N-oxide (0.15 mol) and 100 ml of ethanol was warmed to 60° with stirring for a period of 2 hours. The cooled reaction mixture was poured into 600 ml water with agitation. The precipitated solid was filtered, washed with water and dried. Recrystallization from ethyl acetate yielded 30 gms (50% theory) of white crystalline product. Melting point 90°-92° C.

Analysis based on C₂₅ H₃₇ NOS: Calc: C 75.15; H 9.33; N 3.51; Found: C 75.19; H 9.45; N 3.56

Surprisingly the 2-thio, 2-sulfinyl and 2-sulfonyl pyridine N-oxides disclosed herein have novel and variable plant regulating properties. Through coordination of the proper mode of application, dosage and timing the compounds of this series give such varying responses as growth stimulation, growth retardation and increased productivity.

Particularly interesting retardant and stimulation responses to the application of these compounds include the following areas

Turf

The maintenance of grasses normally employed for functional and esthetic purposes about homes, factories and highways includes regular mowing. For highway and commercial upkeep the service represents a considerable cost factor and to the homeowner a necessary nuisance; at times the turf may turn brown temporarily and unwanted root retardation results. To date turf control has been attained to a certain degree with maleic hydrazide but pronounced browning of the top and unwanted root retardation result. The compounds employed in this invention show unique properties in that the turf top growth is retarded without losing the desirable greenness, and root growth in many cases actually shows enhancement yielding a healthier sod.

The turf species of interest include Manhattan rye grass, Jamestown chewings fescue, Colonial bent, Kingston bent, Bermuda, Baron bluegrass and St. Augustine.

Preferred pyridine N-oxide derivatives which can be employed as turf retardants in accordance with the invention include:

No.

109*: 2-(1-[2,5-dimethylphenyl]ethylsulfonyl)pyridine N-oxide

35*: 2-(1-phenylethylsulfonyl)pyridine N-oxide

105: 2-(1-[4-methylphenyl]ethylsulfonyl)pyridine N-oxide

42: 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide

139**: 2-(1-[2,4,6-trimethylphenyl]ethylsulfonyl)pyridine N-oxide

31: 2-(2,4,6-trimethylphenylmethylsulfonyl)pyridine N-oxide

79: 2-(1-[4-chlorophenyl]ethylsulfonyl)pyridine N-oxide

14: 2-(2,5-dimethylphenylmethylsulfonyl)pyridine N-oxide

57: 2-(2,4-dichlorophenylmethylsulfinyl)pyridine N-oxide

138: 2-(2,3,6-trimethylphenylmethylsulfonyl)pyridine N-oxide

6: 2-(3,4-dimethylphenylmethylsulfonyl)pyridine N-oxide

68**: 2-(2-methylphenylmethylsulfinyl)pyridine N-oxide

27: 2-(2-methylphenylmethylsulfonyl)pyridine N-oxide

142: 2-(2,3,6-trimethylphenylmethylsulfinyl)pyridine N-oxide

128: 2-(2-oxo-2-[2,5-dimethylphenyl]ethylsulfinyl)pyridine N-oxide

The turf retardants described herein are highly active on the variety of turf grasses when applied in dosages of 0.125 to 8 pounds per acre. The compounds may be formulated as liquid or impregnated granule for easy application or in any of a number of other forms as known to the art. The formulations may contain more than one of the described pyridine N-oxide derivatives, other active retardants or synergists.

Cereal Grains

The dual response to retardation and stimulation is of value on cereal grains (particularly wheat, as well as barley, rye, oats, rice, etc.) to produce a shorter plant with a larger number of seed heads per plant by promoting increased tillering. The overall results are to reduce possibility for lodging with increased productivity.

Preferred 2-pyridine N-oxide derivatives which can be employed as plant regulators on wheat or other cereal grains in accordance with the invention include:

No.

14: 2-(2,5-dimethylphenylmethylsulfonyl)pyridine N-oxide

6: 2-(3,4-dimethylphenylmethylsulfonyl)pyridine N-oxide

109: 2-(1-[2,5-dimethylphenyl]ethylsulfonyl)pyridine N-oxide

Sugar Producing Species

Increase in productivity of sugar producing species, such as sugar beets and sugar cane, is a valuable aspect of the invention. Thus, for example, it has been demonstrated that treatment of sugar beets with the claimed compounds results in increased beet weight. To exemplify this, sugar beets were planted in the field at Bethany, Connecticut. 2-(2,6-Dichlorophenylmethylsulfinyl)pyridine N-oxide (Compound 42) was applied as a soil treatment at 4 and 8 pounds per acre at the end of July when the beets were about half grown. About one month later the effect of the treatment on photorespiration was determined by enclosing a large leaf of a plant in a plastic chamber, impermeable to CO₂. Air was aspirated from the chamber at intervals and the CO₂ level determined by infra red absorption of the gas. At equilibrium the beets treated with the compound at 4 pounds per acre reduced the CO₂ level by 35% when compared to the untreated control exposed to the same conditions. The CO₂ level at 8 pounds per acre was reduced by 36% when compared to the control. At harvest there was a yield increase of 8 and 12% at 4 and 8 pounds per acre respectively, when compared to the controls.

Preferred 2-pyridine N-oxides employed as a beet root stimulant in accordance with the invention include:

No.

42*: 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide

68: 2-(2-methylphenylmethylsulfinyl)pyridine N-oxide

131: 2-(2-oxo-2-[2,5-diisopropylphenyl]ethylsulfinyl)pyridine N-oxide

140: 2-(2-nitrophenylmethylsulfonyl)pyridine N-oxide

115*: 2-(1-[2,5-dimethylphenyl]octylthio)pyridine N-oxide

122: 2-(1-[2,5-dimethylphenyl]dodecylthio)pyridine N-oxide

Legumes

The employment of the compounds of this invention on soybeans and other legumes such as beans, peanuts, alfalfa and clover, makes it possible to increase the efficiency of the plant and thereby vastly increase productivity. This is accomplished without altering the normal growth significantly. To exemplify this the Corsoy variety of soybeans was planted in the field at Bethany, Connecticut. When the plants had completed setting of pods, 2-(1-phenylethylsulfonyl)pyridine N-oxide (Compound 35) was sprayed at 2000 parts per million to wet the foliage. About one month later one of the plants in the treated plot was enclosed in a plastic which is not permeable to CO₂. Air was aspirated from the plastic chamber at intervals and the CO₂ level determined by infra red absorption of the gas. At equilibrium the CO₂ level was reduced by 45% when compared to an untreated control plant. This reduction in photorespiration was accompanied by an increase in yield of the harvested soybeans by 6.0%.

Preferred 2-pyridine N-oxides which can thus be employed as productivity enhancers in accordance with the invention include:

No.

35:* 2-(1-phenylethylsulfonyl)pyridine N-oxide

42*: 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide

75: 2-(2-fluorophenylmethylsulfinyl)pyridine N-oxide

68: 2-(2-methylphenylmethylsulfinyl)pyridine N-oxide

27: 2-(2-methylphenylmethylsulfonyl)pyridine N-oxide

96: 2-(4-cyanophenylmethylsulfinyl)pyridine N-oxide

57*: 2-(2,4-dichlorophenylmethylsulfinyl)pyridine N-oxide

83*: 2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide

50*: 2-(2,5-dimethylphenylmethylsulfinyl)pyridine N-oxide

67: 2-(3,4-dimethylphenylmethylsulfinyl)pyridine N-oxide

79: 2-(1-[4-chlorophenyl]ethylsulfonyl)pyridine N-oxide

114: 2-(1-[2-naphthyl]ethylsulfonyl)pyridine N-oxide

128: 2-(2-oxo-2-[2,5-dimethylphenyl]ethylsulfinyl)pyridine N-oxide

2: 2-(phenylmethylthio)pyridine N-oxide

Cotton

In order to facilitate mechanical harvesting it is desirable to reduce the height of the cotton plant to decrease the possibility of lodging. The action of the compounds of this invention, when employed as a foliar spray, terminates apical growth. This termination of growth, once the desired number of bolls has formed, prevents the formation and setting of additional bolls which never mature resulting in lower crop yields.

Field tests have shown that 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide (Compound 42), for example, terminates growth of cotton, promotes maturity of the bolls for earlier harvest and causes young squares to abscise. These are the preferred feeding sites of the boll weevil and pink bollworm, hence their elimination reduces the desirability of this plant for these insects.

High rates promoted abscission of the leaves and prevented regrowth of the axillary buds. This response is desirable for mechanical harvesting of the mature cotton.

Productivity of plants or the production of dry weight per unit of ground area is primarily determined by the total CO₂ assimilated during photosynthesis, minus the CO₂ released as photorespiration. The invention makes it possible to markedly reduce photorespiration, hence improve productivity of plants. Productivity by the following plants can be improved: vegetables such as lettuce, beans, spinach; cereals such as wheat, oats, barley, rice; tobacco, hay grasses, sugar beets, cotton and sunflower.

Promotion of inhibition of axillary buds growth can be useful for control of suckers on tobacco, prevention of sprouting of root crops such as potatoes, beets and carrots.

The promotion of abscission can be useful as a harvest aid for cotton, the mechanical harvesting of fruits such as citrus and cherries.

The promotion of tillering and reduction of height of grain can be useful in prevention of lodging and increasing yield of oats, barley, rye and rice.

The promotion of root growth can increase yields of such underground root crops as beets, carrots and potatoes.

Preferred pyridine N-oxide derivatives which can thus be employed as growth terminators in accordance with the invention include:

No.

61: 2-(phenylmethylsulfinyl)pyridine N-oxide

63: 2-(3-methylphenylmethylsulfinyl)pyridine N-oxide

10: 2-(4-chlorophenylmethylthio)pyridine N-oxide

60: 2-(4-methoxyphenylmethylsulfinyl)pyridine N-oxide

42*: 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide

121: 2-(3,4-dichlorophenylmethylsulfinyl)pyridine N-oxide

109: 2-(1-[2,5-dimethylphenyl]ethylsulfonyl)pyridine N-oxide

83: 2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide

58: 2-(2-phenylethylsulfinyl)pyridine N-oxide

Formulations of the compounds for use in this invention can be prepared in conventional ways. They include dusts, granules, pellets, solutions, suspensions, emulsions, wettable powders, emulsifiable concentrates, oil suspensions, dispersions to include flowable formulations, for example the active ingredient suspended either in oil or water. Formulations also include slow release compositions as a part of any of the following procedures and also include encapsulation of the active ingredient. Many of these may be applied directly to the seed, soil or to the plants. Sprayable formulations can be extended in suitable media and used at spray volumes of from a few pints to several hundred gallons per acre. High strength concentrates are primarily used as intermediates for further formulation. The formulations, broadly, contain about 0.5% to 99% by weight of active ingredient(s) and at least one of (a) about 0.1% to 50% surfactant(s) and (b) about 0.5% to 99% solid or liquid diluent(s). More specifically, they will contain these ingredients in the following approximate proportions:

    ______________________________________                                         Percent by Weight                                                                          Active              Surfac-                                                    Ingredient                                                                              Diluent(s) tant(s)                                        ______________________________________                                         Wettable Powders                                                                             20-90       0-89      1-10                                       Oil Suspensions,                                                               Emulsions, Solutions                                                           (including Emulsifi-                                                           able concentrates)                                                                            5-50      40-95      0-50                                       Aqueous Suspensions                                                                          10-50      40-90      1-50                                       Dusts          1-25      70-99      0-5                                        Granules and Pellets                                                                          1-95       5-99      0-15                                       High Strength Con-                                                             centrates     90-100      0-10      0-5                                        ______________________________________                                    

Lower or higher levels of active ingredient can, of course, be present depending on the intended use and the physical properties of the compound. Higher ratios of surfactant to active ingredient are sometimes desirable, and are achieved by incorporation into the formulation or by tank mixing. Lower concentrations of active ingredient can aid in accurate application at the very low rates reached for this invention. Sprayable and dust formulations are preferred.

Typical solid diluents are described in Watkins, et al., "Handbook of Insecticide Dust Diluents and Carriers", 2nd Ed., Dorland Books, Caldwell, N.J. The more absorptive diluents are preferred for wettable powders and the denser ones for dusts. Typical liquid diluents and solvents are described in Marsden, "Solvents Guide", second edition, Interscience, New York, 1950. Solubility under 0.5% is preferred for suspension concentrates; solution concentrates are preferably stable against phase separation at 0° C. "McCutcheon's Detergents and Emulsifiers Annual", Allured Publ. Corp., Ridgewood, N.J., as well as Sisely and Wood, "Encyclopedia of Surface Active Agents", Chemical Publ. Co. Inc., New York, 1964, list surfactants and recommended uses. All formulations can contain minor amount of additives to reduce foam, caking, corrosion, microbiological growth, etc.

The methods of making such formulations are well known. Solutions are prepared by simply mixing the ingredients. Fine solid compositions are made by blending and, usually, grinding as in a hammer or fluid energy mill. Suspensions are prepared by wet milling (see, for example, Littler, U.S. Pat. No. 3,060,084) or by blending liquids, inert ingredients and previously ground dry active ingredients, followed by a dispersion cycle. Granules and pellets may be made by spraying the active material upon preformed granular carriers or by agglomeration techniques. See J. E. Browning, "Agglomeration", Chemical Engineering, Dec. 4, 1967, pp. 147 ff. and "Perry's Chemical Engineer's Handbook", 4th Ed., McGraw-Hill, N.Y., 1963, pp. 8-59 ff.

For further information regarding the art of formulation, see for example:

H. m. loux, U.S. Pat. No. 3,235,361, Feb. 15, 1966, Col. 6, Line 16 through Col. 7, Line 19 and Examples 10 through 41.

R. w. luckenbaugh, U.S. Pat. No. 3,309,192, March 14, 1967, Col. 5, Line 43 through Col. 7, Line 62 and Ex. 8, 12, 15, 39, 41, 52, 53, 58, 132, 138-140, 162-164, 166, 167, 169-182.

H. gysin and E. Knusli, U.S. Pat. No. 2,891,855, June 23, 1959, Col, 3, Line 66 through Col. 5, Line 17 and Examples 1-4.

G. c. klingman, "Weed Control as a Science", John Wiley and Sons, Inc., New York, 1961 pp. 81-96.

J. d. fryer and S. A. Evans, "Weed Control Handbook", fifth edition Blackwell Scientific Publications, Oxford, 1968, pp. 101-103.

Typical formulations are shown in the following examples. All percentages are by weight.

FORMULATION A

    ______________________________________                                         Wettable Powder           Percent                                              ______________________________________                                         Compound 16               40                                                   dioctyl sodium sulfosuccinate                                                                            1.5                                                  sodium ligninsulfonate    3                                                    low viscosity methyl cellulose                                                                           1.5                                                  attapulgite clay          54                                                   ______________________________________                                    

Thoroughly blend the ingredients then pass through an air mill to produce an average particle size under 15 microns. Reblend and sift through a U.S.S. No. 50 sieve (0.3 mm opening) before packaging.

All compounds of the invention may be formulated in the same manner.

FORMULATION B

    ______________________________________                                         High Strength Concentrate Percent                                              ______________________________________                                         Compound 42               98.5                                                 silica aerogel            0.5                                                  synthetic amorphous fine silica                                                                          1.0                                                  ______________________________________                                    

Blend and grind the ingredients in a hammer mill to produce a high strength concentrate essentially all passing a U.S.S. sieve (0.3 mm openings). This material may then be formulated in a variety of ways.

FORMULATION C

    ______________________________________                                         Dust                     Percent                                               ______________________________________                                         high strength concentrate                                                      formulation B            25.4                                                  pyrophyilite powdered    74.6                                                  ______________________________________                                    

Thoroughly blend the incredients and package for use.

FORMULATION D

    ______________________________________                                         Aqueous Suspension        Percent                                              ______________________________________                                         Compound 139              25                                                   hydrated attapulgite clay 3                                                    crude calcium ligninsulfonate                                                                            10                                                   sodium dihdrogen phosphate                                                                               0.5                                                  water                     61.5                                                 ______________________________________                                    

Grind the ingredients together in a sand mill until the solid particles have been reduced to diameters under 10 microns.

FORMULATION E

    ______________________________________                                         Oil Suspension             Percent                                             ______________________________________                                         Compound 184               25                                                  polyoxyethylene sorbitol hexaoleate                                                                        5                                                  highly aliphatic hydrocarbon oil                                                                          70                                                  ______________________________________                                    

Grind the ingredients together in a sand mill until the solid particles have been reduced to under about 5 microns. The resulting thick suspension may be applied directly, but preferably after being extended with oils or emulsified in water.

Illustrative plant regulant responses for typical 2-thio, 2-sulfinyl and 2-sulfonyl pyridine N-oxides of the formula stated above are shown in Table II, where plant regulant responses are indicated by the symbols defined at the beginning of Table II.

                  TABLE II                                                         ______________________________________                                         Plant Regulators                                                               RW      = retards wheat >30% 6000 ppm                                          RT      = retards turf >50%/8.5#/A                                             RC      = retards cotton >30%                                                  RS      = retards soybeans >30%                                                STR     = stimulates turf roots >25%                                           SSB     = stimulates sugar beets >25%                                          WT      = wheat tillering                                                      P       = enhances production of soybeans >50%                                  ##STR5##                                                                      No.  n     R.sub.1   R.sub.2      Activity                                     ______________________________________                                         1    1     H         2,2-dichlorocyclo-                                                                          RT, RC                                                            propyl                                                    2    0     H         phenyl       P, RC                                        3    2     H         1-methyl-2,2-dichloro-                                                                      RC                                                                cyclopropyl                                               4    2     H         phenyl       RT                                           5    0     H         1-naphthyl   RT                                           6    2     H         3,4-dimethylphenyl                                                                          RT, WT                                       7    2     H         4-methylphenyl                                                                              RT                                           8    2     H         4-chlorophenyl                                                                              RT                                           9    2     H         1-naphthyl   RT, RW                                       10   0     H         4-chlorophenyl                                                                              RC                                           11   0     H         4-methylphenyl                                                                              RC                                           12   1     H         4-chlorophenyl                                                                              RT, RC                                       13   0     H         2,5-dimethylphenyl                                                                          RT                                           14   2     H         2,5-dimethylphenyl                                                                          RT, RW                                       15   2     H         4-nitrophenyl                                                                               RS                                           16   2     H         cyclohexyl   RS                                           17   2     H         2,2-dichlorocyclo-                                                                          RT                                                                propyl                                                    18   0     H         2-ethylphenyl                                                                               RT                                           19   1     H         methyl       RW                                           20   2     H         2-benzothiazole                                                                             RS                                           21   0     H         2-methylphenyl                                                                              RT, RS                                       22   2     H         2-chlorophenyl                                                                              RT                                           23   0     H         2-chlorophenyl                                                                              RT                                           24   2     H         n-undecyl    RC                                           25   0     H         n-decyl      RS                                           26   0     CH.sub.3  phenyl       RS                                           27   2     H         2-methylphenyl                                                                              STR, RT, P, RS                               28   2     H         x, y-dichloro-                                                                              RT                                                                phenyl                                                    29   0     H         2,6-dichlorophenyl                                                                          RT                                           30   0     H         2,4,6-trimethyl-                                                                            RT                                                                phenyl                                                    31   2     H         2,4,6-trimethylphenyl                                                                       RT, P, RW                                    32   2     H         2,6-dichlorophenyl                                                                          RT, RW                                       33   2     H         3-trifluoromethyl-                                                                          RW                                                                phenyl                                                    34   2     H         2,4-dichlorophenyl                                                                          RW                                           35   2     CH.sub.3  phenyl       STR, RT                                      36   0     H         2,4-dichlorophenyl                                                                          RT                                           37   2     H         2-methoxy-5-nitro-                                                                          RT                                                                phenyl                                                    38   0     H         3,4-dimethylphenyl                                                                          RT                                           39   2     H         isopropenyl  RT                                           40   0     H         benzyl       RT                                           41   2     H         benzyl       RT                                           42   1     H         2,6-dichlorophenyl                                                                          RT, RW, RS                                   43   0     H         2-fluorophenyl                                                                              RT, RC, RW                                   44   2     H         2-chloro-3,4-dioxy-                                                                         P, RW                                                             methylene                                                 45   2     H         2-fluorophenyl                                                                              RT, RW                                       46   2     ethyl     n-butyl      RT, RC                                       47   2     H         2-ethylphenyl                                                                               RT, RW                                       48   2     methyl    n-butyl      RT                                           49   2     cyclohexyl           RT                                             50   1     H         2,5-dimethylphenyl                                                                          RT, P, RW                                    51   0     methyl    methyl       RT                                           52   0     H         2-cyanophenyl                                                                               RS                                           53   2     cycloheptyl          RW                                             54   2     H         2-cyanophenyl                                                                               RT                                           55   2     methyl    methyl       RT                                           56   0     cycloheptyl          RT                                             57   1     H         2,4-dichlorophenyl                                                                          RT, P, RS, RW                                58   1     H         benzyl       RC, RW, RS                                   59   1     H         3-trifluoromethyl-                                                                          RT, RC, RS                                                        phenyl                                                    60   1     H         4-methoxyphenyl                                                                             RT, RC                                       61   1     H         phenyl       RT, RS                                       62   0     H         3-methylphenyl                                                                              RT, RS                                       63   1     H         3-methylphenyl                                                                              RT, RC, RS                                   64   2     H         3-methylphenyl                                                                              RT, P, RS, RW                                65   1     H         2,4,6-trimethyl-                                                                            RT, P, RW, RS                                                     phenyl                                                    66   1     H         2-chlorophenyl                                                                              RT, RS                                       67   1     H         3,4-dimethylphenyl                                                                          RT, P, RW, RS                                68   1     H         2-methylphenyl                                                                              STR, RT, SSB,                                                                  RS                                           69   1     H         2-cyanophenyl                                                                               STR, RT, RS,                                                                   RW                                           70   1     H         4-methylphenyl                                                                              RT, RS                                       71   2     H         3-fluorophenyl                                                                              RT, RC                                       72   1     H         4-fluorophenyl                                                                              RT, RS, RW, RC                               73   2     H         4-fluorophenyl                                                                              RT, RC                                       74   1     H         3-fluorophenyl                                                                              RT, RS, RW                                   75   1     H         2-fluorophenyl                                                                              RT, P, RS                                    76   1     H         oxophenyl    RT, RW                                       77   2     H         oxophenyl    RS                                           78   0     methyl    4-chlorophenyl                                                                              RS                                           79   2     methyl    4-chlorophenyl                                                                              STR, RT, P, RS,                                                                RW                                           80   0     propyl    phenyl       P, RC, RS                                    81   0     methyl    4-methylphenyl                                                                              RC                                           82   0     H         pentachlorophenyl                                                                           RC                                           83   0     H         2,3,6-trichloro-                                                                            RT, P, RC, RW                                                     phenyl                                                    84   0     H         4-cyanophenyl                                                                               RT, P                                        85   0     H         oxo-4-(2,2-dichloro-                                                                        RT                                                                cyclopropyl)phenyl                                        86   0     H         oxo-2,4-dimethyl-                                                                           RT                                                                phenyl                                                    87   0     methyl    2-naphthyl   RT, RS                                       88   2     H         2-methoxy-5-methyl-                                                                         RT, RS, RW                                                        phenyl                                                    89   2     H         2-bromo-5-methoxy-                                                                          RT, RS, RW.                                                       phenyl                                                    90   2     H         pentachlorophenyl                                                                           RS, RW                                       91   1     H         pentachlorophenyl                                                                           RT, RS, RW                                   92   2     H         2,3,6-trichloro-                                                                            RT, RS, RW                                                        phenyl                                                    94   1     H         2,3,6-trichloro-                                                                            RT                                                                phenyl                                                    95   2     H         4-cyanophenyl                                                                               RT, RW                                       96   1     H         4-cyanophenyl                                                                               RT, P                                        97   2     H         oxo-2,4-dimethyl-                                                                           RT, RW                                                            phenyl                                                    98   1     H         oxo-2,4-dimethyl-                                                                           RT, RW, RS                                                        phenyl                                                    99   0     methyl    2,5-dimethylphenyl                                                                          P, RW, RS                                    100  0     methyl    4-bromophenyl                                                                               RW                                           101  2     H         2,5-diisopropyl-                                                                            RW                                                                phenyl                                                    102  1     H         2,5-diisopropyl-                                                                            STR, RT, RW                                                       phenyl                                                    103  1     H         oxo-4-(2,2-dichloro-                                                                        RS                                                                cyclopropyl)phenyl                                        104  2     propyl    phenyl       RS, RW                                       105  2     methyl    4-methylphenyl                                                                              RT, RS, RC, RS                               106  2     methyl    4-methylphenyl                                                                              RT                                           107  2     methyl    2-thienyl    RW, RS                                       108  2     methyl    4-fluorophenyl                                                                              RT, RW, RS, RC                               109  2     methyl    2,5-dimethylphenyl                                                                          RT, RC, RW, RS,                                                                WT                                           110  0     ethyl     phenyl       RS, RW                                       111  0     methyl    3,4-dichlorophenyl                                                                          RC                                           112  0     H         3,4-dioxymethylene-                                                                         RC                                                                phenyl                                                    113  1     methyl    4-fluorophenyl                                                                              RC, RS, RW                                   114  2     methyl    2-naphthyl   STR, RT, P                                   115  0     n-heptyl  2,5-dimethylphenyl                                                                          STR, RT, SSB                                 116  1     methyl    4-bromophenyl                                                                               RS, RC                                       117  2     methyl    4-bromophenyl                                                                               RW, RS, RC                                   118  2     ethyl     phenyl       RC, RS                                       119  0     H         oxo-2,5-dimethyl-                                                                           P                                                                 phenyl                                                    120  1     H         oxo-4-fluorophenyl                                                                          RW, RC                                       121  1     H         3,4-dichlorophenyl                                                                          RC, RS, RW                                   122  0     n-undecyl 2,5-dimethylphenyl                                                                          SSB, RW                                      123  0     H         3-bromophenyl                                                                               P, RC, RW                                    124  2     H         3-bromophenyl                                                                               STR, RT                                      125  1     H         3-bromophenyl                                                                               STR, RT, RC,                                                                   RW, RS                                       126  2     methyl    3,4-dichlorophenyl                                                                          STR, RT                                      127  2     H         oxo-2,5-dimethyl-                                                                           RT, RC, RW                                                        phenyl                                                    128  1     H         oxo-2,5-dimethyl-                                                                           RT, P, RC, RS,                                                    phenyl       RW                                           129  1     H         3,4-dioxymethylene-                                                                         RT, RC, RS, RW                                                    phenyl                                                    130  2     H         3,4-dioxymethylene-                                                                         STR, RT, RC,                                                      phenyl       RS, RW                                       131  1     H         oxo-2,5-diosopropyl-                                                                        STR, RT, SSB,                                                     phenyl       RC                                           132  2     H         2-propionic acid                                                                            RC                                           133  1     methyl    oxo-phenyl   RC, RS, RW                                   134  2     methyl    oxo-phenyl   RW                                           135  0     H         2,3,6-trimethyl-                                                                            RS                                                                phenyl                                                    136  0     H         2-nitrophenyl                                                                               RC, RW                                       137  0     H         4-(2,2-dichloro-                                                                            RW                                                                cyclopropyl)phenyl                                        138  2     H         2,3,6-trimethyl-                                                                            STR, RT, RS,                                                      phenyl       RW                                           139  2     methyl    2,4,6-trimethyl-                                                                            RT                                                                phenyl                                                    140  2     H         2-nitrophenyl                                                                               STR, RT, SSB                                 141  1     H         2-nitrophenyl                                                                               STR, RT, RW,                                                                   RS                                           142  1     H         2,3,6-trimethyl-                                                                            RT, RW                                                            phenyl                                                    143  2     H         2-methyl(1-naphthyl)                                                                        RW                                           144  1     H         2-methyl-(1-naphthyl)                                                                       RT                                           145  1     phenyl    2-methylphenyl                                                                              RW                                           146  2     H         1-iodophenyl RS, RW                                       147  1     H         1-iodophenyl RT, RW, RS                                   148  2     methyl    4-nitrophenyl                                                                               RT, RW                                       149  2     H         4(2,2-dichloro-                                                                             RT                                                                cyclopropyl)phenyl                                        150  1     H         4(2,2-dichloro-                                                                             RT, RS                                                            cyclopropyl)phenyl                                        151  2     methyl    1-naphthyl   RT, RW                                       152  1     methyl    1-naphthyl   RW                                           153  0     H         3,4-dimethoxyphenyl                                                                         RT, RW                                       154  1     H         3,4-dimethoxyphenyl                                                                         RW, RS                                       155  2     H         3,4-dimethoxyphenyl                                                                         RW, RS                                       156  2     methyl    2,5-diethylphenyl                                                                           RW, RW                                       157  0     methyl    2,5-diisopropyl-                                                                            RS                                                                phenyl                                                    158  1     cyclopentyl          RT                                             159  2     cyclopentyl          RT                                             160  2     H         2,5-dimethoxyphenyl                                                                         RT, RS, RW                                   161  1     H         2,5-dimethoxyphenyl                                                                         RS, RW                                       162  1     H         2-ethoxyphenyl                                                                              RS                                           163  2     H         2-ethoxyphenyl                                                                              RW, RS                                       164  0     methyl    2-chloro-4-methyl-                                                                          RS                                                                phenyl                                                    165  2     methyl    2-chloro-4-methyl-                                                                          RS, RW                                                            phenyl                                                    166  1     methyl    2-chloro-4-methyl-                                                                          RS, RW                                                            phenyl                                                    167  0     methyl    2-chloro-5-methyl-                                                                          RT                                                                phenyl                                                    168  2     methyl    2,5-diisopropyl-                                                                            RT                                                                phenyl                                                    169  0     H         2,3,5,6-tetrachloro-                                                                        RT                                                                4-methylphenyl                                            170  1     H         2,3,5,6-tetrachloro-                                                                        RT, RS, RW                                                        4-methylphenyl                                            171  2     H         2,3,5,6-tetrachloro-                                                                        RT                                                                4-methylphenyl                                            172  0     methyl    2,5-dichlorophenyl                                                                          RT                                           173  1     methyl    2-chloro-5-methyl-                                                                          RS, RW                                                            phenyl                                                    174  2     methyl    2-chloro-5-methyl-                                                                          RS, RW                                                            phenyl                                                    175  1     methyl    2,5-dichlorophenyl                                                                          RT, RW                                       176  2     methyl    2,5-dichlorophenyl                                                                          RT, RW, RS                                   177  1     methyl    2,4,5-trimethyl-                                                                            RW, RT                                                            phenyl                                                    178  2     methyl    2,4,5-trimethyl-                                                                            RS, RW, RT                                                        phenyl                                                    179  1     methyl    2,3,4-trimethyl-                                                                            RC, RW, RT                                                        phenyl                                                    180  2     methyl    2,3,4-trimethyl-                                                                            RC, RW, RT                                                        phenyl                                                    181  1     methyl    2,3,4,5-tetramethyl-                                                                        RT                                                                phenyl                                                    182  2     methyl    2,3,4,5-tetramethyl-                                                                        RC, RW, RS, RT                                                    phenyl                                                    183  1     H         3,4,5-trimethoxy-                                                                           RC, RS                                                            phenyl                                                    184  2     H         3,4,5-trimethoxy-                                                                           RT                                                                phenyl                                                    185  1     H         9-anthryl    RT                                           186  0     H         2-thienyl    RC                                           187  1     H         2-thienyl    RS, RW                                       188  2     H         2-thienyl    RC, RS, RW                                   189  1     methyl    phenyl       RT, RW                                       190  1     methyl    2,5-dimethylphenyl                                                                          RT, RC, RW                                   191  1     methyl    4-chlorophenyl                                                                              RT, RC, RW                                   192  2     methyl    2,4-dichloro-3-                                                                             RC, RW                                                            methylphenyl                                              193  1     methyl    2,4-dichloro-3-                                                                             RW                                                                methylphenyl                                              194  0     methyl    benzyl       RC                                           195  2     isobutyl  2,5-dimethylphenyl                                                                          RT                                           196  2     methyl    benzyl       RT                                           197  1     methyl    benzyl       RT                                           198  0     methyl    2,5-dichlorothienyl                                                                         RT                                           199  0     benzyl    2,6-dimethylphenyl                                                                          RC                                           200  0     H         4-vinylphenyl                                                                               RW                                           201  1     H         4-vinylphenyl                                                                               RW, RS                                       202  0     methyl    4-biphenyl   RW                                           203  0     methyl    4-phenoxyphenyl                                                                             RW                                           204  2     methyl    4-phenoxyphenyl                                                                             RC                                           205  0     methyl    2-methyl-5-iso-                                                                             RC                                                                propylphenyl                                              206  2     methyl    2-methyl-5-iso-                                                                             RC, RW                                                            propylphenyl                                              207  0     methyl    5-indanyl    RC, RW                                       208  2     methyl    5-indanyl    RC                                           ______________________________________                                    

preferred compounds employed in the method of the invention are those of formula I above wherein

n is 0, 1 or 2

R₁ is hydrogen, methyl or n-heptyl

R₂ is phenyl or phenyl substituted with from 1 to 3 substituents which may be the same or different and are selected from the group consisting of methyl and chlorine.

Particularly preferred are the following:

Compound 35, 2-(1-phenylethylsulfonyl)pyridine N-oxide, especially for use on turf and legumes such as soybeans.

Compound 109, 2-[1-(2,5-dimethylphenyl)ethylsulfonyl]pyridine N-oxide, especially for use on turf.

Compound 42, 2-(2,6-dichlorophenylmethylsulfinyl)pyridine N-oxide, especially for use on legumes such as soybeans, cotton, peanuts, and sugar-producing species such as sugar beets.

Compound 50, 2-(2,5-dimethylphenylmethylsulfinyl)pyridine N-oxide, especially for use on legumes such as soybeans.

Compound 57, 2-(2,4-dichlorophenylmethylsulfinyl)pyridine N-oxide, especially for use on legumes such as soybeans.

Compound 83, 2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide, especially for use on legumes such as soybeans.

Compound 115, 2-(1-[2,5-dimethylphenyl]octylthio) pyridine N-oxide, especially for use on sugar-producing species such as sugar beets.

New compounds of formula II above that are particularly remarkable for their unusual activity are:

No.

80: 2-(1-phenylbutylthio)pyridine N-oxide

115: 2-(1-[2,5-dimethylphenyl]octylthio)pyridine N-oxide

122: 2-(1-[2,5-dimethylphenyl]dodecylthio)pyridine N-oxide

The following examples will serve to illustrate the practice of the invention in more detail.

EXAMPLE I TURF

The test solutions are prepared by dissolving 10 milligram samples in acetone followed by dilution to 100 ml with water and two drops of "Tween 20" (trademark; polyoxyethylene sorbitan monooleate). The solutions are equivalent to 8.5 pounds per acre/100 ml which could be subsequently diluted to 4.25 and 2.12 pounds per acre equivalents.

A. The turf grass species are grown in three inch styrofoam cups six inches deep. The grass is planted and held in the cups until a good root system develops to fill the cup. The test solution of the desired concentration is then poured on the soil surface as a drench. About one week later the turf is clipped back to a uniform height. Percent growth inhibition is calculated by Abbotts formula compared to regrowth of untreated controls.

B. To observe root growth and top growth simultaneously a 3 inch black plastic pipe 12 inches long was cut longitudinally to a length of 11 inches to permit removal of a half section. A piece of copper screening was cemented to the bottom to confine the soil. The removable section was secured with a plastic strap.

The experiments are carried out by removing a treated plug from its styrofoam cup and inserting it into the tube containing eight inches of untreated soil. The tubes are placed in racks at a 45° angle on a greenhouse bench with the removable section down to permit the roots to grow along its surface. The tops are clipped one week after treatment and regrowth is measured at the same time as root observations are made.

The following table illustrates the results obtained from typical experiments.

    __________________________________________________________________________     % TOP                                                                          GROWTH INHIBITION     % ROOT GROWTH INHIBITION*                                Compound St.                                                                               Blue-                                                                              Ber-     St.                                                                               Blue-                                                                              Ber-  Leaf                                     No.   Rye                                                                               Aug                                                                               Fesc                                                                               muda                                                                              Ave.                                                                              Rye                                                                               Aug                                                                               Fesc                                                                               muda                                                                              Avg.                                                                              Color                                    __________________________________________________________________________     109   93 100                                                                               100 100                                                                               98 0  0  -50 0  -13                                                                               Good                                     139   73 100                                                                               100  75                                                                               87 0  0  +50 0  +13                                                                               Good                                      35   87  78                                                                                79 100                                                                               86 0  0  -35 0  -9 Good                                      79   93 100                                                                               100  25                                                                               80 -10                                                                               0  0   +25                                                                               +4 Good                                      68   47  56                                                                                86  83                                                                               68 0  -50                                                                               0   -50                                                                               -25                                                                               Good                                     Maleic                                                                         Hydrazide                                                                            80  67                                                                                75  79                                                                               75  100                                                                               100                                                                              100  100                                                                               100                                                                              Poor                                     __________________________________________________________________________      Dosage 2.12 pounds/acre                                                        *(-) inhibition.                                                               (+) stimulated.                                                          

EXAMPLE II COTTON

The test solutions are prepared by dissolving 0.3 gm of compound in 10 ml of acetone and diluting to 100 ml with water containing 0.3% "Triton X100" (trademark; isooctylphenyl polyethoxy ethanol). Dilution to 200 ml yields solutions of 1500 ppm.

Cotton plants are grown in six inch pots to a height of twelve inches. Replicated plants are then sprayed to the drip point at dosages of 3000 and 1500 ppm. Height measurements are made two months after treatment.

The following table illustrates typical results obtained by the treatments.

    ______________________________________                                         Compound                                                                               Dosage   % Height                                                      No.     ppm      Reduction                                                     ______________________________________                                         42      1500     50        2-(2,6-dichlorophenyl-                                                         methylsulfinyl)pyridine                                     3000     45        N-oxide                                             61      1500      7        2-(phenylmethylsulfinyl)                                    3000     27        pyridine N-oxide                                    121     1500     34        2-(3,4-dichlorophenyl-                                                         methylsulfinyl)pyridine                                     3000     36        N-oxide                                             58      1500     34        2-(phenylethylsulfinyl)                                     3000     32        pyridine N-oxide                                    10      1500     22        2-(4-chlorophenylmethyl-                                    3000     37        thio)pyridine N-oxide                               60      1500     44        2-(4-methoxyphenylmethyl-                                   3000     32        sulfinyl)pyridine N-oxide                           ______________________________________                                    

EXAMPLE III SOYBEANS

The test solutions are prepared by weighing out 0.3 gm of test compound and dissolving in 10 ml of acetone. Dilution with water containing 125 ppm of "Tween 20" to 800 ml gave a test solution of 375 ppm.

Corsoy variety of soybeans are grown in six inch pots containing 2 plants per pot. When the plants are in the trifoliate stage replicates were sprayed to the drip point. Approximately one month later the number of pods per plant are counted and compared with the controls.

The following table illustrates typical results obtained.

    ______________________________________                                         Compound        Average number                                                 No.             pods/plants   % Increase                                       ______________________________________                                         57              11.0          134                                              83              10.7          128                                              96              10.0          113                                              67              9.3            98                                              Untreated controls                                                                             4.7           --                                               ______________________________________                                          Dosage at 375 ppm                                                        

EXAMPLE IV WHEAT

The test solutions are made up by weighing out the compound and dissolving in 10 ml of acetone followed by dilution in water to give equivalents of 4 and 6 pounds/acre.

Waldron wheat is grown in six inch pots with three plants per pot. When the plant has reached the early boot stage the solution is poured into the saucer. The soil completely absorbs the liquid by this treatment. After three months the mature wheat was measured and the number of heads per plant counted.

The following table illustrates results obtained from these tests.

    ______________________________________                                         Compound  Dosage     %           Avg.No.mature                                 No.       lb/acre    Retardation heads/plant                                   ______________________________________                                          6        4          10          5.4                                                     6           9          6.7                                           14        4          51          4.3                                                     6          58          3.4                                           Untreated --         --          3.0                                           ______________________________________                                    

EXAMPLE V SUGARBEETS

The test solutions are prepared by dissolving the weighed compound in 10 ml of acetone followed by dilution to 100 ml with water containing 2 drops of "Tween 20".

Sugarbeets are planted in six inch pots in the greenhouse at one per pot. When the tops become five inches tall and possess sixteen leaves a soil drench is applied to replicates at rates of 1 to 2 pounds per acre. Approximately three months later the roots are freed from soil, weighed and compared to controls.

The following table illustrates results obtained.

    ______________________________________                                                    Dosage     Avg. % increase in beet                                  Example    ·/acre                                                                           root weight over controls                                ______________________________________                                          68        2          124                                                      140        2          105                                                      131        1          117                                                      115        1           76                                                      ______________________________________                                    

EXAMPLE VI PEANUTS

The major production of peanuts in the United States is with runner types. Each branch from the main stem produces a flower at each node, starting at the main stem. The flower then produces a peg which penetrates the soil to form the peanut pod. This is a continuous process until harvest. Pods formed during the latter part of the summer do not mature by harvest time. It is desirable to reduce number of pods formed so that those already formed will mature to maximum size.

To demonstrate the ability of the present compounds to reduce pod formation on runner type peanuts the following emulsifiable concentrate was prepared:

    ______________________________________                                         2-(2,6-dichlorophenylmethyl-                                                   sulfinyl) pyridine N-oxide                                                                             12 grams                                               emulsifying agent       10 grams                                               ethylene dichloride to 100 ml                                                                         122.39 grams.                                           ______________________________________                                    

The emulsifying agent was a nonionic-anionic blend of alkyl phenoxy polyethoxy ethanols and organic sulfonates (Emulsifier AH861[trademark], Rohm & Haas); the concentration of the invention compound was 1.0 pound per gallon.

Florigiant variety of Virginia type runner peanuts (Arachis hypogaea L.) were planted in deep flats, four plants per flat; 74 days later they were sprayed to runoff with formulations made by diluting the above concentrate to 1250 and 2500 ppm. Seven weeks later the plants were harvested and the number of pods and pegs on each node were counted. The following table summarizes the data. It is apparent that the number of pods and pegs were reduced by the treatment.

    ______________________________________                                         Total Number of Pods and Pegs                                                  on Four Peanut Plants                                                                 Node Number                                                                    1   2     3     4   5   6   7   8   9   10  Total                       ______________________________________                                         Check pods   26    20  18  10  3   1   0   0   0   0                                                      78                                                                              pegs  5 13  9  7 11  8 7 2 7 1 70                                                         148                                                                Treat-                                                                         ment pods 15 22 11  1 1 3 0    53                                              1250                                                                           ppm pegs  4  4  1  1 0 3 2    15                                                           68                                                                 Treat-                                                                         ment pods 22 14  5  1 0 2     44                                               2500                                                                           ppm pegs  4  5  8  1 1 0     19                                                            63                                      ______________________________________                                     

We claim:
 1. A method of regulating the natural growth or development of plants which comprises applying to said plants an effective non-herbicidal plant-regulating amount of a 2-thiopyridine N-oxide compound of the formula ##STR6## wherein: R₁ is hydrogen, C₁ to C₁₅ alkyl, phenyl or benzyl;R₂ is hydrogen, C₁ to C₁₂ alkyl, C₁ to C₄ alkenyl, C₂ or C₃ alkoxycarbonyl, C₅ or C₆ alicyclic, phenyl provided R₁ is not phenyl, phenyl substituted with from 1 to 3 substituents which may be the same or different and are selected from the group consisting of C₁ to C₃ alkyl, halogen, cyano, nitro, C₁ or C₂ alkoxy, phenoxy, dioxymethylene and 2,2-dichlorocyclopropyl; and phenyl substituted with 4 to 5 substituents which may be the same or different and are selected from methyl and chlorine; 1-methyl-2,2-dichlorocyclopropyl, 2,2-dichlorocyclopropyl, naphthyl, 9-anthryl, 5-indanyl, 4-biphenylyl, 2-benzothiazolyl, 2-thienyl or benzyl; R₁ and R₂ may be joined together in the form of a polymethylene chain --(CH₂)_(m) -- where m is 3, 4 or 5 to form a carbocyclic ring; and when R₁ is hydrogen or methyl R₂ can be the radical ##STR7## where y is 0, 1 or 2 and the X's are the same or different and are selected from C₁ to C₃ alkyl, halogen, and 2,2-dichlorocyclopropyl.
 2. A method as in claim 1 in whichR₁ is hydrogen, methyl or n-heptyl R₂ is phenyl or phenyl substituted with 1 to 3 substituents which may be the same or different and are selected from the group consisting of methyl and chlorine.
 3. A method as in claim 2 in which the said compound is applied to turf.
 4. A method as in claim 2 in which the said compound is applied to soybeans.
 5. A method as in claim 2 in which the said compound is applied to cotton.
 6. A method as in claim 2 in which the said compound is applied to sugar beets.
 7. A method as in claim 2 in which the said compound is applied to peanuts.
 8. A method as in claim 1 in which the said compound is applied to sugar beets, and the said compound is selected from the group consisting of2-(1-[2,5-dimethylphenyl]octylthio)pyridine N-oxide and 2-(1-[2,5-dimethylphenyl]dodecylthio)pyridine N-oxide.
 9. A method as in claim 8 in which the said compound is2-(1-[2,5-dimethylphenyl]octylthio)pyridine N-oxide.
 10. A method as in claim 1 in which the said compound is applied to soybeans, and the said compound is selected from the group consisting of2-(phenylmethylthio)pyridine N-oxide and 2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide.
 11. A method as in claim 1 in which the said compound is applied to cotton, and the said compound is selected from the group consisting of2-(4-chlorophenylmethylthio)pyridine N-oxide and 2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide.
 12. A method as in claim 1 in which the said compound is2-(2,3,6-trichlorophenylmethylthio)pyridine N-oxide.
 13. A method as in claim 1 in which the said compound is2-(1-[2,5-dimethylphenyl]octylthio)pyridine N-oxide. 